What Chemicals Should I Put In My Fish Tank?

After partial water changes, the water quality of your aquarium might change. Beneficial bacteria might be lost following changes to your aquarium water and algae growth might suddenly become an issue. There is a large variety of chemicals which could be put into your tank, however, not all of them are actually safe for a fish tank. Some can even kill the fish when done incorrectly with new fish.

So before we answer the question, what chemicals should I put in my fish tank? Let’s look at what chemicals you definitely should not put in your fish tank. Chlorine and chloramine typically found tap water and city water is detrimental to the health of your pet fish. This should be removed from a water aquarium prior to settling your live fish in it. Any types of pesticides, chlorine, fuel, liquid fertiliser and other toxic chemicals are also a no-no.

It is really difficult figuring out which ones you really need for your aquarium with so many chemicals on the market. But don’t worry, after reading this, you will be able to easily tell which chemicals are safe for your saltwater aquarium and what you need to avoid.

Below is a list of the safe and important chemicals you can add to your fish tank.

• A Dechlorinator

Chemicals like chlorine, ammonia, and heavy metals that are harmful to your fishes are present in our regular tap water. So to ensure the good health of your fishes, your tap water must be treated before being poured into your fish tank. If the tap water is left untreated, the chemicals in it can irritate and can even injure your fishes, therefore causing discomfort and compromising the breathing function of their gills. This could kill them.

To completely eliminate chlorine and ensuring proper a water care process is in place, a dechlorinator can be used.


Dechlorination of your tap water can be done with sulphur dioxide, sodium bisulphite (NaHSO3) or sodium metabisulphite (Na2S2O5). Scientifically speaking, about 0.9 mg of sulphur dioxide or 3.6 mg of sodium bisulphite or 1.38 mg of sodium metabisulphite (65% w/w SO2) removes 1.0 mg of chlorine or 0.742 mg of monochloramine.

Actually, at least more sulphur dioxide or twice the stoichiometric quantity for sulphites would be required for dechlorination. Dechlorination reaction is generally fast and takes usually less than 1 minute to complete. Sodium thiosulphate (Na2S2O3), which is sometimes used to dechlorinate chlorinous waste discharges in the environment, takes longer, typically up to 5 minutes.

You may also dechlorinate your tap water by filtering it through GAC or by using ammonia or hydrogen peroxide. GAC can be used to protect chlorine sensitive reverse osmosis membranes. GAC speeds up a dechlorination reaction and is not consumed by chlorine, but it should be replaced on a regular basis due to adsorption of other material, which can make it harmful to your fishes.

• Methylene Blue

This is another important chemical required for the survival of your fishes. Methylene Blue is a common constituent of many chemical products used in aquariums. This chemical has been found to prevent and treat fungi infection, hinder fungal growth on fish eggs, and cause a decrease in nitrite levels.

Methylene Blue does not just carry out these functions; it, in fact, does them very well. Although methylene blue is so great, treating your water with products containing Methylene Blue too frequently can result in water that is bad for your aquatic pets. Methylene Blue does not only destroy bad bacteria, but also the good ones necessary for the nitrogen cycle.

If there is no good bacterial in your tank’s water, there is a high chance of the Ammonia levels in your tank rising to a dangerous level. When this dangerous increase is taking place, it gives off very few warning signs. You probably won’t notice until your fishes start dying. So if you don’t regularly test your tank’s water, ammonia can almost be impossible to detect, therefore acting as a quiet killer to your fishes.

Chemicals that contain Methylene Blue should only be used in critical situations, and only as prescribed by a Vet. Instead of frequently using this chemical, you could decide to more frequently change your fish tank water, as this will equally control the level of bacterial in the tank.

Excessive use of Methylene Blue will scatter the nitrogen cycle which is very important for your fishes and this will result in the accumulation of ammonia in your tank.

• Stress Coat

This is another type of de-chlorinator, It contains a lot of aloe which helps your fishes build strong slime coat covering, which is a fish’s major defence against infection and disease. This slime coat acts as a guard against disease-causing organisms in the fish’s external environment and as a barrier to prevent loss of internal electrolytes and body fluids.

An example of a natural irritant to a fish’s skin is aloe. If a fish touch an aloe, it will feel irritated and begin scratching its body against things within the tank, thereby stimulating the skin build a thicker protective slime coat. It is very safe to use on your aquatic pets and can be bought from a local pet store.

However, you are not advised to use this product in a hatchery.

• Alkaline buffers

Acidic water is not good for a fish tank; it can lead to the death of your fishes. If you find that the pH of your fish tank is lower than 7 then an alkaline chemical is needed.

There are a few ways to raise the pH of your tank. One way is to get yourself powdered alkaline buffers online or at your local pet store.

Another way is by adding a bit of buffer to your tank, by doing so; you can keep your tanks water at the pH level you want without disrupting other chemical constituents in your aquarium or harming the fish. Many aquarists advice you remove your fishes from the tank temporarily before adding any chemical to the water.

If you can’t get your hands on a buffer or alkaline powder, some of the most common bases like baking soda can be added to the aquarium. If you wish to use baking powder, add about 1 teaspoon per 5 gallons of water to the tank. This should result in an incremental change that leads to a healthier pH level.

In conclusion, not all chemicals are bad for your fish tank. But what you should note is that some of the chemicals you are allowed to add to your tank should be added at safe concentrations to ensure the survival of your fishes.