Quick Stats
Minimum Tank Size: 29 Gallons (110 Litres)
Care Level: Easy
Water Conditions: 7.0-8.5 pH and Hard Water
Temperature: 70-79 °F (21-26 °C)
Maximum Size: 5 inches (20 cm)
The black molly (Poecilia sphenops) is small live bearer fish, that ranks among the most popular fish in the aquarium hobby. It is native to both South America and Central America, and can be found from Venezuela in the south, to Mexico in the north. It is also found on several Caribbean islands, and in recent years has become established as an invasive species in Japan, parts of the United States and in scattered pockets in Eastern Europe.
In the wild they primarily inhabit freshwater streams, but they can also be found living in brackish coastal sea waters and swamps. There is a mistaken belief in the hobby that black mollies are a brackish water fish, and while they are highly adaptable to salt water conditions, they prefer a freshwater environment.
They remain a relatively small fish in the home aquarium, and males will grow to a maximum of 3 inches (7.5 cm), while the females can grow up to 5 inches (12.5 cm) in length. Most mollies will live around three years in captivity, though some well cared for mollies can live for as long as five years.
Housing
Black mollies can be sensitive to poor water conditions, so they should be provided with a spacious aquarium which allows for more stable water parameters. While the minimum tank size for a small group of mollies is 29 gallons (110 litres), that doesn’t take into account the vast quantity of fry that inevitably arrive. If you want a tank where the fry can be grown out to a reasonable size, the minimum tank size rises to 45 gallons (170 litres).
It’s important that any tank containing mollies maintains a very strict ratio of the sexes. There should be at least two females for every male, and many people recommend at least a three to one ratio. The reasons for this ratio is that males relentlessly attempt to mate with females, and by providing more females, you ensure that no one female receives all of the males attention. Should you keep a lower ratio, the females will quickly become stressed from the constant mating attempts, and will often fall ill and may even die.
It is generally recommended that any tank containing mollies be heavily planted. The adult mollies will appreciate the planted environment, but more importantly, the plants will help with the fry survival rate. Some easy to care for plants that you can add to a mollies tank are Amazon sword plants, hygrophila polysperma, Java ferns, Java moss, water sprite and water wisteria.
Even though numerous articles recommend adding salt to a mollies aquarium, this is unnecessary if they are kept in alkaline, hard water. There are numerous studies that show mollies will be just as healthy if kept in aquarium without salt, though there is some evidence that salt can be beneficial to them if they are not kept in their preferred water conditions.
Filter
When choosing a filter for mollies, the best choice is generally a hang on back filter. While a canister filter is usually a superior filter, it tends to be overkill with mollies, and the price tag is usually at least double that of a hang on back filter.
I strongly recommend choosing an Aquaclear Power Filter
Feeding
Mollies are omnivores, and feed on invertebrates, plant matter and detritus in the wild. This diet should be replicated as closely as possible in the home aquarium, and they should be fed a high quality flake food, along with regular feedings of live or frozen foods and vegetables.
Unlike many other fish, vegetables are absolutely essential to a mollies health, and they should be offered blanched zucchini medallions, shelled peas and cucumber medallions at least once a week. If you can’t offer vegetables, they should be fed Hikari Algae Wafers
Their favorite live foods are mosquito larvae (illegal to culture in some areas), bloodworms, blackworms, daphnia and brine shrimp. They have similar tastes in frozen foods, and they can be fed frozen blackworms, daphnia, bloodworms and blackworms.
Breeding
Black mollies are easy to sex, and the females will be larger than the males and have a triangular anal fin. Meanwhile, the males will be smaller, and have a gonopodium, which is a modified anal fin that serves the purpose of hooking onto the female and depositing sperm.
Breeding will normally take care of itself in a molly tank, and as long as you ensure that you maintain at least a two to one ratio of females to males, you will soon have pregnant mollies. The pregnant mollies can be identified by a dark gravid spot near their anal fin, and a considerably plump stomach.
Black mollies are a live bearer fish, and unlike most other commonly kept fish, they don’t lay eggs. The fry develop inside of the female, and they are born fully formed and swimming. Because of this, they generally have a very high survival rate, though some adult fish may still eat them.
When they mate, the male impregnates the female with a bundle of sperm on his gonopodium, which is delivered to her vent. Once the female is pregnant, the gestation usually take about 7-8 weeks, at which point the female may deliver upwards of one hundred babies. On average, the female will deliver anywhere from 40-100 fry, though you can expect younger female mollies to be on the lower end of that scale.
If you want a high fry survival rate, then the female molly should be removed from the main tank prior to giving birth. While mollies aren’t as predatory as guppies or platies, the adults will still eat many of the fry. After the female has given birth, she should also be removed from the fry tank.
The fry don’t require any special food, and right from birth they can be fed ground up flake food. They will also accept the usual fry foods, and can be fed baby brine shrimp, microworms or one of the many available commercial fry foods.
Illness
Black mollies are a color morph, and unfortunately they tend to be badly inbred these days. Because of their inbreeding, they are susceptible to illness, and aren’t as hardy as they used to be.
When purchasing mollies, always carefully examine the tank in the fish store, and don’t purchase them if there is any trace of illness. While this is true of most fish, it is extra important for mollies since they can often be wiped out by a simple illness.
I have a ten gallon tank, how many Mollies could I place?
Ten gallons is too generally too small for mollies, but if you get shortfin mollies, and really keep on top of maintenance you might make it work with 3-4 mollies. Just make sure you have 1 male and 2-3 female mollies, otherwise you’re going to have problems. And you’ll need to consider what you will do with the inevitable fry, since they will mate eventually.
I bought a male and female because I know the ratio and in less than 24 hours they were both dead 🙁 don’t know if this was the cause of death. don’t know if this was the cause of death
** Sorry did not know the ratio **
An off ration would never kill them that quickly. Was your tank cycled? Were there any sick fish in that tank at the pet store? Were there any signs of illness visible on them? Swollen body? Fungus like growths? Swollen eyes?
No it’s not the cause of death
You need to be careful with water pH levels and change water every two days allowing atleast 10 to 25 percent of the same old water.
I agree with Robert. An off ration would never kill that quickly. I would definitely check for alternative sources to that problem.
Can you give me some pls….i am begging you pls give some of your fishes.
.
Hi there,
We had a beautiful black molly (female); tank parameters —
temperature = 83 degrees
salinity = 1″
NO2 = Oppm
NO3 = Oppm
NH4 = Oppm
pH = 7.4
we have a 50 gallon tank, moderately planted.
we just lost the female this morning; there are 2 males left (we had to other females, who also died)
there were no visible signs of illness; do you have any idea what we could have done/could do differently? I love these fish, and loved that little black molly…we called her Billie Holiday. :-))
Thank you for your time,
All of your parameters look good, and if there were no signs of illness, there’s not much else you could have done. Mollies tend to be fragile sometimes, and occasionally you’ll get a death like that, with no clear signs of why they died. The only possible thing I could think of was that the two males would have likely been harassing her, and she may have become stressed from that. I like to keep at least a 2 to 1 ratio of females to males, so they spread the aggression out a little bit.
I have 76 black molly fry what food I should give them help….
Very finely crushed up flake food would be fine, but you can also try some foods like microworms or baby brine shrimp. However, livebearers fry are large enough that this isn’t really an issue though.
I have 8″ fish bowl how many black Moli I have to put?
Unfortunately, no mollies would be able to live in that. You need an aquarium, a filter and a heater for a molly to survive, and 29 gallons in the absolute minimum for mollies.
We have 2 Mollies and now have 2 babies which are about 4 weeks old and this morning we discovered 2 smaller babies, we have had the fish since the 7 May is it possible we bought 2 females?
Sometimes, mollies can have a gestation period of as little as four weeks, so it may be the same fish giving birth a second time. However, they are pretty easy to sex, and I’ve attached a picture to this comment to help you sex your mollies.
I have 2 male black mollies in a 1 gallon tank with no filter and no heater just rocks and a plant and they are doing just fine so i dont knowwhy the minimum is 29 gallons
They may look fine, but I can guarantee you if you test the water it will have ammonia and nitrites in it. And both of those are toxic to them, and will damage their gills over time. So while they may seem alright, they are most likely suffering, and will have greatly shortened life spans.
Also, a tank like that is not nearly large enough for them to move around in – especially as they grow. They need lots of space to swim, or they will start to fight, and grow fat from inactivity.
Hi! I have four mollies. 3 of them would never keep their distance and swims together all the time but the other one, which is a male, never joins them and just stays to one place and neber leaves. When the other mollies try to get near him he tends to fight them away. He seems to be a loner and very teritiorial. I’m just worried if this is a sign of any possible illness? Thankyou 🙂
Males spend much of their time either trying to mate, or off by themselves. I wouldn’t worry too much about it, unless there are other signs of illness, like a fungus, or bloating. Male mollies just tend to be ornery for the most part.
I have 2 plastic garden tanks in the front garden..the tanks are fully mature little swamps…I installed 4 black mollees…I now have 200 mollees swimming around out front…they are all sizes indeed and very healthy…here in Tx the wild birds storkes, cow birds and giant herons feed on outdoor ponds…most people install colored fish …The bright colors catch the attention of the birds and they are gone in a matter of days…the black mollee does not attract the attention of the predators so they live to a ripe old age..they eat the algae and regular flake food..anyone need some mollees?
That sounds like a pretty cool setup. I always like the natural setups, and I’ve wanted to so something like that in my backyard. If my wife wouldn’t leave me, I’d probably do a simple one in an old pool, but she wants it much nicer than that.
I hope you find someone looking for some black mollies. You should try local forums too, or craigslist. Stuff like that tends to go fast.
what is the salinity level suitable to black mollies? and what is the importance of this fish in our community specially on mosquitoes?
If acclimated to it slowly, they can survive with salinity levels up to 34 ppt (gravity of 1.021 to 1.026). But in my experience, they do best in freshwater, with no salt. However, many people recommend keeping them at a gravity of around 1.003-1.005, although if kept healthy, I find this unnecessary.
I have read in many texts that they do eat mosquito larvae, but nothing has ever indicated it’s a main component of their diet. I don’t know much more than that.
I have 6 Lyretail black mollies iin a 65 gal. tank and 3 cory cats and a ploco. The mollies really enjoy the Algae rounds I give the cats and the ploco. No little ones yet 3 males and 3 females.
I bought a black molly two months ago and have a 5 gallon aquarium. Heat filter all the works. Two weeks after having her she had 15 babies. I had literally just gotten rid of 8 of them three weeks ago and the other 7 died. I woke up yesterday and have over 30 babies in my tank. What do I do? I can’t find a pet store to take them and the pet stores that will say they need to be 3-4 weeks old.
That’s one of the most difficult aspects of keeping livebearers and cichlids: What do you do with all the babies? But probably one of the best way to get rid of fish is to join the local forums, or fish groups. There are always people looking to take extra fish.
Can anyone tell me if a male platinum molly can fertilize a female gold dust molly’s eggs?
I dont know. Thanks.
My black molly just gave birth to seven babies, I got the net for them and fed them ground flakes, some of the babies are lying on the bottom of netting, they are still alive but is there anything I can do to help?
It sounds like there is something wrong with the water. I’d do a small water change immediately, and try to get as much waste out of the net as possible.
Hello,
I am having two mollies and I have kept them in fish bowl . I am having a problem It seems to be that they are trying to eat But they aren’t eating
They’re probably not doing so well in the fish bowl. It can be difficult at time to keep mollies healthy in a filtered, heated aquarium. You should really consider upgrading their tank as soon as possible.
But when you say they’re trying to eat, what does that mean? Is something like white fuzz blocking their mouth?
No , They are trying it goes inside their moth and then comes out again . After a lot of time I thought of giving them smaller pieces of food and after a lot of effort they ate it ! 🙂
One more doubt Can u suggest me some air pumps for my mollies (which are in fish bowl) You know which are Cheap , Quiet and are of Good Quality ! 🙂 And answer for your Question I don’t have lot of money to spend I have a bowl and I am trying to adjust with it. 🙂
The best thing I can recommend it a sponge filter. A small one should fit in your bowl, and you need an air pump with it. It should come to less than 20 dollars though, and will give some filtration to the tank.
As for the the food thing, I don’t know. I’ve seen them unable to eat from illnesses, but this is weird. What are you feeding them?
1359.07 Indian Rupees that’s a lot man common over India it’s a lot !
Can U just anything from eBay.in or amazon.in or Filpkart Please…………… 🙂
and I am feeding them something kind of 2 mm to 3 mm sized circle foods 🙂
I have a 100 litre tank with 2 male and 7 female mollies all are adults and theres no vegetation in the tank only a terra-cotta pot and a coconut she’ll cave. With two air stones and a 1500l/hr filter. They are new to the tank now my question is how much do I feed them. I have been feeding them flakes twice a day. Now how to measure the flakes. I heard about the two minute rule but some don’t even come to surface in the two minutes while others finish it, really confused.
Also I have a stone substrate I don’t want to plant the tank this early , I’m a new aquarist so give me some suggestions.
I personally like to use the three minute rule and if you find some aren’t coming to the surface, use something to announce it’s feeding time. I like to lightly tap on the glass and after a few days, they should all be trained to recognize the sound of dinner time. That way you don’t have to risk overfeeding.
As for the plants, why don’t you want to plant them this early? They’re very beneficial in young aquariums and can help protect against ammonia spikes. Granted, there are less nitrates for them, but most will still do well.
I meant early for me, task of caring for the plants for a beginner. Can you suggest some pants growing on Rock substrate without need of monitoring co2?
What sort of rocks are you talking about? Large river type rocks, or smaller gravel?
Small river gravel 3 to 5mm I plan on changing the substrate totally after 6 to 8 months when I ‘ll have plenty of spare time at hand. May be a proper planted aquarium
Hi, so this is the thing, I have a 10 gallon tank, not a lot of stuff in it to keep it a little roomy. I really want to get a (black short-finned molly) but I also heard that they like being with other molles and fish’s.
Can/Will a molly do fine in a 10 gallon? And is so. How many can I put?
Thanks!
Black mollies especially are very sensitive to water conditions, and are very difficult to keep in a 10 gallon aquarium. They aren’t necessarily a shoaling fish, and will do well in small numbers, but I like to usually keep a male and some females together. A few males will definitely cause problems if kept together.
I have 2 female mollies in a 1.5 gallon tank but i am planning to upgrade it to a 5 or 10 gallon tank but my mollies are aggresive to each other.
And it is making me worry because every fish that i kept in the 1.5 gallon tank are not aggressive to each other. I even seperate them for a few hours and when i put the other one back to the tank, she is still aggressive to the other one. What should i do about them??
The main problem is really the size of the tank. They need space to escape from each other and 1.5 gallons is just far too small. Once you upgrade, the problems should be reduced. Also, you should try to upgrade to at least 29 gallons in the future.
My molly has a swollen eye. Can I do anything to help it?
Is it only one eye? Usually, if it’s only one eye, then it’s either an injury or poor water quality. First off, check the water chemistry and make sure nothing is off. Then add a small amount of salt to the water (1 tablespoon per 5 gallons), which helps with healing – but be careful if you have life plants.
If that doesn’t work, or it spreads to both eyes, then you should consider using antibiotic food and perhaps moving the fish to a quarantine tank, as it can be contagious.
Let me know how it goes.
I got one
male Molly and one female and a little bottom feeder in a 30 gallon tank, is that good?
As long as it’s the short-fin molly variant, you should be fine tank size wise. But I would recommend adding at least one more female, otherwise the male will constantly harass the lone female in the tank.
I have 1 male and 5 female mollies ………..is it fine ?
That’s a good ratio to have, and the male will definitely be kept busy going from female to female. You shouldn’t have any problems with those numbers.
I had a black male molly and a orange female. The female had 4 babies then the black one died. Why do you think it died.the 4 babies are fine . About 3 weeks old now
It’s tough to say with fry. It could be water quality, it could be lack of food, or it could be something else entirely. Water is usually the culprit, as molly fish fry are incredibly sensitive to water quality. Even with absolutely pristine aquariums, it’s not uncommon to lose a few of them.
If I were you, I’d focus on maintenance to keep the water quality as good as possible for the remaining molly fry.
Can molly withstand 38 degree celsius temperature??
Maybe for a short while, but they’ll quickly start to suffer and you’ll probably encounter low oxygen levels. How is the water that hot?
I have one black Mollie,one demation two gold and black. The black is male seems to run the others wild. What to do?
How many males and females are there?
What to do?
Help!! I just bought a black mollie female… had her not even 8 hours… and now i have 15 or more babies in my tank!! I have been able to remove 15 of them without disturbing the tank to much… but im leaving on a trip and i have no idea on how to make sure they survive usually i leave feeder tabs cause i only have 2 fish….
Also need advise i had a big belly molly and a red tail Platt but she murdered him wouldnt stop attacking him… well ive put her back in the tank with the new female and she has been biting her to and her scales are being abused…. i thought tropical fish were not aggressive please help!!!
It’s tough with newborn fry as they need really need to be fed twice daily. Do you have anyone who could feed them for you?
As for the platy, they can be nippers at time. How large is the tank and how is it setup?
Per recommendation of an employee at Valley Stream PetSmart, I purchased 3 Black Molly’s & 1 Dalmatian Molly (xmas gift, two for each child) for a 5 gallon tank. We were going to get goldfish, but he recommended a selection of fish that my kids them chose from. 24 hours later, the tank became super cloudy. The next day, one Black Molly died. I googled about aquarium cloudiness, and went to a different petsmart to pick up a water clarifier and another fish (didn’t tell the kids that one died). Explained the situation to an employee and he was shocked that I’d be recommended that many mollies in a small tank. Even stated that he wouldn’t be surprised if more died. He recommended water changes and to not get the clarifier. I bought it anyway (had a coupon, only paid $1) and the tank is still cloudy. Haven’t done a water change yet because I don’t have the supplies. But what should i get for my tank? I have a filter, water conditioner, water clarifier, 3 plastic plants, plastic rock, 9 lbs gravel. Do I need a heater, live plants? Help a newbie out please 😊
First of all, did you wash the gravel before using it? Some of the cloudiness might be from that. But more likely, it’s from a bacterial bloom. Before you place fish in an aquarium it needs to be cycled, otherwise toxic chemicals build up and can kill the fish.
At this point, all you can do is do daily water changes (around 25% or so) and add fast growing aquatic plants like hornwort. The plants will use some of the toxic chemicals for growth, so and provide oxygen for the tank. Also, but a test kit and find out what the ammonia and nitrites levels are in the aquarium. That way you’ll know what you’re dealing with.
And to be honest, it will be a struggle to keep the mollies alive in a tank that size, but if you work hard, they should be able to last for a while. But you probably want to upgrade in the near future if you want to keep them.
Thanks for your reply! Yes i cleaned the gravel on Christmas Eve, ran the filter. We didnt purchase and add fish until Dec 26th (almost 48 hours later). I thought that would be enough time to cycle. The tank didnt cloud until Dec 28th. I know I overfed them the first night, so I thought that might be the issue, but it hasnt cleared. I havent bought the tools to siphon the water yet. I will be purchasing tonight from amazon.
Also, I read somewhere to add some salt to the freshwater. And I was wondering if i need a heater? I think my tank may be too cold. And what foods besides the tropical flakes should I feed them?
Unfortunately, it takes about 2 weeks to cycle, so 48 hours wouldn’t have done. And they definitely need a heater if you want them to be healthy; Room temperature water will never be warm enough for them. As for the salt, it does seem to help mollies, but be careful since many fish can’t tolerate it. A good safe starting point for aquarium salt is to add one level teaspoon per gallon. Salt helps to reduce stress in fish by aiding osmoregulation.
As for food, I would just stick with flakes until you get it under control. But once it’s under control, add small pieces of lightly blanched zucchini or cucumber, making sure to remove any leftovers the next morning to prevent the water from fouling.
Highly agree with the ratio of sexes in tanks before one year i bought alsmost 24 mollies in 10 gallons of water tank but they all dead after some times so i got the good point today
I have two pregnant black mollies, one has fungus on her mouth. I think she will be delivering soon, but I want to treat her in this fungus cure. With her being due any day now would that be a good thing to do or hold off till she have the fry and then treat her. please help don’t want to lose her.
You definitely want to treat the black molly as soon as possible. Fungus spreads quickly and it needs to be dealt with. I would recommend using a hospital tank if possible, as you don’t want the fry in the same tank as the medicine.
Thank you so much. But what about the other fish. Do u think they will need treatment. Or just look for sign n go from there. Will put her in hospital tank today
Just keep a close eye on the other fish. Hopefully it hasn’t spread, but be prepared to treat the other fish.
My daughter bought some fish last week and one was a black molly. Two days later there were babies. They all were swimming around and eating and now 3-4 days later we don’t see them. Do they eat them even days later after they are born?
Unfortunately, if a fish is small enough to fit in another fish’s mouth, it will get eaten eventually. Floating plants and lot of thick plants will help to keep the babies safe, though a breeding net works best.
I’m setting up a 75 gallon community tank and have always loved Black Mollies but have never had much luck with them. Any suggestions on water conditions and tank mates would be greatly appreciated. I live in East Tennessee and do not have a water softener.
Mollies do best in hard water, so don’t worry about not having a water softener. And mollies can be a very difficult fish to keep. The first step is to find healthy fish – something that can be very difficult. Always check out the tank at the store before purchasing them. If there are any dead fish or sick fish in the tank, don’t buy from there. Black mollies are extremely sensitive to illness.
After you have some healthy fish, make sure you tank is fully – and properly – cycled. I find dense live plants help to keep the water quality up in newly cycled tanks. Any, and I mean any, fluctuations in the water quality will likely kill mollies.
When it comes to tankmates, you have numerous options. I personally like keeping them with corydoras catfish (if the water isn’t too hard), zebra danios, other livebearer fish, and any non-aggressive species of tetra (once again, if the water isn’t too hard).
I hope this helps.
hi ,
i have one black molli and a golden fish in my tank…is it ok to keep them together…or i need to get extra black molli
Hi guys, I have a question. I have angelfish and I tried to feed him, but it seems that my fish is not eating. I tried to feed him with all types of fish foods, but Im losing hope. I did some research on my own and found out that feeding fish pot oil does give their metabolism a boost. Like this article about a marijuana strain https://www.ilovegrowingmarijuana.com/purple-urkle/. If this is true I can’t find any solid conclusive evidence that speaks to its efficacy. Any personal experience or testimonial would be highly appreciated. Thanks
I can’t speak to cannabis, but usually it means the fish is wild caught and not accustomed to eating prepared foods. I would start with lives foods – usually black worms, wingless fruit flies, worms, and gut loaded brine shrimp (rinse off the salt first) – since all of these are easily available in most areas. As the fish start to accept the live food, slowly start to mix in the dried fish food until they start accepting it. If you can’t find any of those lives foods, let me know, and I’ll see what else I can think of.
Why does my molly put food in his mouth then spit it out?
My Orange color ballon mollies male are doing breeading with same color females although i have black and white females also they are not spawning with them are they only breeding according to colors ?
That should only be a coincidence, as mollies are indiscriminate breeders. Given enough time, they should spawn with each other.
My black molly had 4 babies but it’s taking her forever so I moved her to a new tank and she still is not done having babies.
I looked it up she is supposed to have over 100 babies?
The number of babies can vary by quite a lot, giving birth between 30-100 babies. For a young females, it’s not unusual for it to be on the lower end of those numbers.
One more question will the molly fish breed on its own. (black molly).
Because I have the female (mom) with the baby in a 10-gallon tank.
Hi my parents say I can only have a 3 1/2 gallon tank but I would like three mollies is that OK ?
Unfortunately, mollies grow far too big for a tank that size. If you really want a live-bearer, you could potentially fit a few guppies in there, but it would be very tight and you’d have to be careful to always watch the water quality.
Hi Robert
My two black mollies are pregnant (1 being very big pregnant) so I moved them both to a 20gall tank. Do they “nest” prior to giving birth? I saw her digging into the stones. How will I know when it’s going to happen lol? My first time of having fry!
And are they usually territorial? My one male has disappeared so I concluded that they got rid of him…
Thx
Hey Bonnie,
Mollies don’t nest before giving birth, but the females will usually try to find a somewhat secluded spot. And among these fish, it’s the male who is territorial and not the females. In fact, the females will do their best to avoid to male and his ‘attention’.
We started a small tank with one male mollie and three females. They all died one at a time. In a month only one was left I think the male. So we got four new fish and put them in with him. Tetras. There is one left. He seems to harass them. Is he trying to mate with them? Can I switch him to my tank with large goldfish?
I doubt that he’s trying to mate. Often male mollies are aggressive, especially without any females around. And goldfish and mollies have very different water requirements—mollies are tropical while goldfish are a cold water fish. It would be best if you could keep them apart. Probably the best way to deal with the aggression is to make some changes to your tank. Try adding some real or fake plants and decorations. Then set it up to divide your aquarium into ‘areas’ where the fish can swim without seeing the other fish. Usually, when fish lose line-of-sight with another fish, they break off any aggression.