The root causes for algae overgrowth lie within one of the three factors algae requires for growth: water, light, and nutrients. Before treating your aquarium for algae, it's important to determine what the underling cause is. This aquarium algae primer describes each source, how to treat according, and includes preventative measures to help avoid future algae overgrowth.
A word of caution - before using chemical treatments, keep in mind that if algae growth is not severe, manually removing it and performing regular aquarium maintenance is your best approach to managing algae issues. Use of chemical treatments for any aquarium problem should be considered carefully, because the side effects can cause more problems than they solve.
During that time, it is critical that water tests be performed regularly to determine the level of ammonia in the tank. If the ammonia reaches dangerous levels, steps must be taken to quickly reduce it. Water changes will help, but if the ammonia is extremely high, an ammonia binder should be used to bring ammonia down. Ammonia binders are available in a liquid form, or in the form of filtration media. For rapid reduction of critically high ammonia, use a liquid binder. Filter media form is useful when levels are elevated, but not immediately critical.
A newly set up aquarium is not the only situation in which ammonia can become elevated. If fish die and are not promptly removed, or the filter fails for a period of time, or if the tank is not maintained well, ammonia levels can rise. Regular water testing will help detect ammonia spikes. Anytime something happens, such as a prolonged power outage, or sudden fish death, I recommend testing for ammonia immediately, then again several days later. If ammonia is detected, continue testing daily until the ammonia drops. If the ammonia rises to potentially harmful levels, take action to lower it.
However, salt also has a down side. Scaleless fish, such as many in the catfish family, do not tolerate salt well. Live plants are also fairly intolerant of salt. Before using salt, consult the salt in freshwater article for best practices and dosing methods.
However, there are times when it is necessary to alter the pH. Lowering the pH is best achieved by using filtered water that is low in mineral content. Blackwater treatments will lower pH and soften the water, but if the source water has a high buffering capacity, the pH will rise again. Using filtered water that is has a low buffering capacity will ensure the pH remains stable in the lower range you desire.
Raising the pH requires the opposite strategy, increasing the buffering capacity of the water. While products such as pH UP may temporarily raise the pH, keeping it there is the problem. When attempting to raise the pH in a freshwater aquarium, always use a method that increases the buffering. Crushed coral is an excellent means for accomplishing this. Buffering additives together with a pH adjusting product will work as well. The key to any pH change is to avoid a sudden change that will not remain stable. Frequent pH changes do more harm than a pH that is slightly off from the optimal range.
phosphate water test When phosphates are elevated, water changes and tank maintenance will help reduce them. The use of phosphate reducing products such as specialized filter media, or phosphate control additives will help bring phosphate levels down and reduce algae growth.
Most tap water conditioners also contain an agent to support the slime coat of your fish, which is important when fish are stressed. Even though you may not think so, every time you change water, perform maintenance, or make any changes in the aquarium, it stresses the fish. Although it may be only a mild stress, it can affect the health of your fish.
A number of water conditioners also include an agent to convert ammonia to the non-toxic ammonium. Some will also advertise that they neutralize nitrite and nitrate. However, none of them can do that instantly. The best they can do is promote the biologicals that are part of the nitrogen cycle. Given time, those biologicals will break down toxins, but it won't happen immediately.