First off, it’s usually not recommended to alter the pH levels in an aquarium, but there are certain circumstances where you may have no choice but to lower the pH. It could be because you’re trying to breed a fish like neons that only spawn in soft water, or perhaps you’re trying to keep a wild-caught fish that simply won’t survive in water with a high pH.
But before you even think about changing the pH of an aquarium, I have to state this is for advanced aquarists only. Rapid pH swings are deadly to fish, and nothing will wipe out an aquarium faster than pH shock.
And don’t think this is something that you can ‘set-and-forget’: the pH must be monitored constantly, and at the bare minimum, the pH will have to be checked and adjusted after every water change.
Also, if you’re trying to lower the pH, you need to be careful about what you add to the aquarium. Many substrates, such as crushed coral and gravel, along with rocks, including limestone and dolomite, will raise the pH in an aquarium. If you need to lower the pH, you need to be careful what ornaments and substrate you use, and the tank should be planned as a low pH tank right from the start.
What is a Low pH Level?
For those not familiar with the pH scale, a low pH level indicates a higher level of acidity in the water. On the opposite end of the scale, a high pH level indicates a higher level of alkalinity in the water. Usually, a ‘normal’ pH level falls somewhere between 5.5-7.5 pH, though many sources of the water fall outside that ‘normal’ band of pH.
Fish and pH Levels
Since most fish are farm raised or bred in tanks these days, they can adapt to a wide variety of pH levels – far more than their wild caught counterparts are able to tolerate. Because of this, it’s extremely rare to find yourself in a situation that you would need to alter the pH of an aquarium, unless the water you’re using is at one of the extreme ends of the scale.
And to be honest, if you’re water falls outside the ‘normal’ range, then it’s usually better to choose fish that would thrive in your water, and not try to alter it. For example, the water in my area has an 8.5 pH and is very hard. Because of this, I concentrate on hardwater fish like African cichlids, live-bearers and invertebrates.
But if you’re intent on lowering your pH, below are the best ways to accomplish it.
Most fish-keepers are probably already lowering the pH of their aquarium without even realizing it. Any driftwood added to an aquarium will lower the pH. The wood filters the aquarium water, slowly reducing the pH overtime.
And while it won’t rapidly lower the pH of the water, it does help to keep the levels steady. And without excessive water changes, driftwood will continuously – but very slowly – lower the pH. But don’t expect this to make hard water soft – it will only lower the pH in small increments.
Before adding any driftwood to an aquarium, make sure to soak it for at least two weeks. Otherwise, the tannins from the wood will stain the aquarium water a brownish color. While the tannins are harmless, brown water isn’t the healthiest look for an aquarium. Also, make sure only to use driftwood that you know is safe to use with fish, as certain woods are toxic.
Of all the ways to lower the pH levels in an aquarium, peat moss is the most tried-and-true method. People have been using this since virtually the dawn of fish-keeping, and it does an excellent job lowering the pH of an aquarium. However, like driftwood, it may stain the water a yellowish color, so it’s best to soak it separately for a few days to remove any coloration.
Peat moss can either be added to an aquarium by putting it in a mesh bag, or by placing pellets inside of the filter. Don’t try to add the peat directly to an aquarium as they float and will create a terrible mess. One product that is specifically designed for aquariums is Fluval Peat Granules. I’ve used these in the past to lower my incredibly high pH levels, and they are highly effective.
It should be stressed that peat moss lowers the pH slowly, so don’t expect any rapid changes. Also, excessive water changes can reduce the benefits of peat moss. If you’re actively attempting to lower the pH levels of an aquarium, I would recommend only doing one small water change a week.
The Indian almond leaf (Catappa) is another excellent natural way to lower the pH levels in in an aquarium. It both softens the water and lowers the pH, but like most other natural methods, it can stain the water. Before adding almond leaves to the aquarium, they should be soaked in water for a few days to allow most of the tannins to leach out.
These leaves also have the added benefit of removing toxins from the water, and there is even some evidence these leaves have beneficial health properties for fish. But it’s difficult to find much hard evidence to back this up. Many fish also benefit from leaf litter on the substrate as it recreates their natural habitat and makes them feel more comfortable.
The potential benefits, along with the natural look these leaves give an aquarium, make them an excellent choice for anyone attempting to lower the pH levels in their aquarium. And thanks to Amazon, Indian almond leaves can easily be found now.
Reverse Osmosis Filters
If you’re serious about lowering the pH levels in your aquarium, the best way to go is to use a reverse osmosis filter. While the other methods mentioned will help to lower the pH, they are long term solutions that need careful monitoring, where one too many water changes can undo weeks of work.
A reverse osmosis filter uses a multi-stage system to remove sediment, toxins, heavy metals, and the majority of any water hardness. They produce pure water for aquariums, and if you’re trying to breed fish in soft water, this is absolutely your best bet to keep it stable and clean.
But these systems aren’t cheap, so I would only recommend them for people attempting to breed fish that require soft water, or when you’re keeping delicate and finicky fish that need soft water and near perfect water quality to survive.
One of the simplest methods to lower the pH of an aquarium is to simply decrease the amount of aeration. The more aeration an aquarium has, the higher the pH. If you lower the aeration, the carbon dioxide will rise and the pH levels will lower.
But this can be a dangerous game to play with fish. While some fish need low pH levels, they need oxygen even more. I would only ever attempt this on a sparsely stocked aquarium, and the other methods are much more reliable and less dangerous to your fish.
Test Your Water
If you are actively trying to lower the pH of your aquarium, the best advice I can give you is to test the water regularly. If the pH starts to swing rapidly, or if it starts to get too low, you need to know about it before your fish start going belly up. As stated before, this isn’t something you set-and-forget, because the consequences of it going wrong can be a tank apocalypse.
But if you stay on top of it, and are careful with how you proceed, you can experience breeding fish in soft water– something that makes all the effort easily worth it.