It might not be an obvious thing to consider when you start your aquarium, but you will find that certain fish prefer a different pH. Roughly speaking, the ‘normal’ pH for your tank should vary between 5.5 and 7.5 on the pH scale for freshwater fish; this is approximately the range of normal tap water. Anything lower than 5.5 would be considered acidic, and anything high than 7.5 would be alkaline, but you can find more information in our article on the fish chart pH scale.
It is possible to lower the pH of your tank with chemicals, but many websites and even the US government have released studies listing how toxic common chemicals are to fish. You will find that the vast majority of websites online suggest using natural ways to lower pH first, and that you should only use chemicals as a last resort because they can be too expensive or even kill your fish!
A Word of Guidance
Your fish can become sick or die if you change the pH on your tank too quickly, so adjust it slowly and see how your fish react.
Natural Ways to Lower pH
- Peat Moss
Peat moss is a cheap solution to lowering the pH by filtering contaminants in your water. The one downside to it is that it can cause your water to turn slightly yellow, but if you pre-treat your peat moss in a bucket and pour the water into your tank when doing a partial water change, if will reduce the yellow colour.
Generally speaking, people find peat moss most effective by putting a small amount of moss into a filter or mesh bag, then placing the ball of moss directly into the filter or hiding it somewhere in the tank. The peat moss can last for a year, but to be safe, it is best to change the moss every six or seven months.
This type of soil can be easily found on amazon or your local pet stores, but make sure that it is chemical or additive free to avoid harming your fish. The cheapest way would be to bulk buy some from a gardening store.
- Indian Almond or Oak Leaves
These work in the same way as peat moss, but they will produce a noticeable yellow to red color to the water as they release tannin into it. Again, you can pre-treat them in a bucket and pour the water in during a water change, use a filter bag just like with peat moss or add activated charcoal to help reduce the colour if you don’t like it.
Several reputable sites would actually suggest you leave the leaves free floating or as part of a tank decoration, especially for fish whose wild habitats would naturally contain a lot of leaf litter that they would use to hide or eat.
First, it is important to select the right type of wood. Wood used for reptiles might not be best for your tank as it will contain contains that can harm your fish. As with the other two options, driftwood will release tannin into the water, but it will only change the water color. You can choose to boil your driftwood in salt water, or soak it in water for several days to help reduce discoloration. You should also clean your driftwood before putting it in your tank to make sure you don’t introduce other contaminants into the water.
The best type of wood is something that is coarse and porous as it will absorb the most contaminants. Driftwood also has the benefits of looking attractive and providing places for your fish to hide and generally make them feel more comfortable.
- Reverse Osmosis Systems
This is the most expensive way of lowering your pH as a good system can cost several hundred dollars. It also also more complex to initially set up when compared to the other three methods, though it will likely need less maintenance than peat moss or Indian almond leaves in the long term.
When adjusting your pH for your tank, always use natural methods first as they are both cheaper and have more benefits than just lowering pH. There are systems and chemicals to use, but they would be a last resort due to the price as well as the possible dangers to your fish.