Water and Water Quality

Ordinary tap water is fine for filling up the aquarium as long as you let it sit for several days before adding fish (the chlorine in the tap water will kill the fish). You may also purchase dechlorination solutions at our store. Several drops of the solution in pure tap water is usually enough to dechlorinate the water instantly.

When adding water to the aquarium for the first time, add water that feels cool to the touch, but not cold. Trickle the water in slowly so that you do not disturb the gravel. Pouring water onto a rock will reduce the impact of the flow. Continue adding water until the level is about one inch from the top of the tank. It is a good idea to let the filter run for a week before adding fish to the tank.

Water Quality

Aquarium water quality deteriorates for several reasons. Fish, being living and breathing creatures, obviously produce various waste products that accumulate in the water. Other organic matter, such as uneaten food, decays into substances that can contaminate the water.

Over time, these pollutants may build up in an aquarium to a level that is dangerous to the occupants. In their native environment, fish are protected from this problem by a natural system. The water in a river or lake is continually replenished with fresh rainwater, and different chemical and biological processes remove organic pollutants from the water.

To keep a healthy aquarium, you simply need to understand this natural system and duplicate its effects for your fish.

Prior to the advent of filtration, hobbyists depended on guesswork and trial and error to maintain a balance in the tank. The number and size of fish, the abundance of plants and the ability of snails and other scavengers to consume excess food and other materials in the tank were all taken into consideration. It was a delicate balancing act and not easy to master.

Today's aquarium technology, particularly the filtration systems, eliminates much of the guesswork, labor and problems of keeping fish. Certainly in comparison to keeping fish in a bowl, where all of the water must be changed at least once a week, an aquarium with a filter is more convenient and easier to maintain. Still, filtration systems have limitations.

No matter how sophisticated, a filter can only slow down the rate at which the water in an aquarium becomes polluted. No filter system can actually stop water quality from deteriorating. Filtration is important to maintaining good water quality for the fish, and filters do make it possible to keep more fish in an aquarium.

Success with fishkeeping, however, requires more than a good filter. The true value of filtration is that it helps you maintain good water quality more consistently, but only if some easy-to-follow principles of aquarium care are followed.

The real key to success is found in three basic rules, each formulated to create a stable environment for the fish.

  • Rule one is to not overstock the tank with fish. The more fish there are in an aquarium, the faster the water quality goes down. As noted earlier, the filter only slows this process.
  • The second rule is to not overfeed the fish. The accumulation of uneaten food in the tank will quickly contaminate the water.
  • Rule three is to do frequent partial water changes. This removes pollutants and adds fresh, clean water to the aquarium, helping to maintain a healthy habitat.

If you understand these three rules and the reasoning behind them, you're well on your way to becoming a successful aquarist.

Water Chemistry

To successfully maintain a healthy tank, you need to understand some basic fish tank water chemistry. This will help your fish to not only survive but thrive! Understanding water chemistry basics and regular testing are imperative. Remember, at Bob's Tropical Fish we offer professional water testing free of charge any time you need it.

As part of your initial set up, you might want to purchase kits to test for the following:

  • Ammonia
  • Nitrite
  • Nitrate
  • pH
  • Water Hardness
  • Chlorine/Chloramine


Testing for ammonia is a must. Ammonia will be elevated during the startup cycle in a new tank. Ammonia can also be elevated in mature tanks if the water is not changed regularly, filters are not kept clean, if the tank is overstocked, or if medication is used that disrupts the biological cycle.

In an established tank, an ammonia test should be performed and recorded in a log once a month. Anytime you have sick fish, or a fish death, you should immediately test for ammonia. Ammonia is extremely toxic to fish and any detectable amount of ammonia should be addressed swiftly.


During the startup of a new tank, nitrite levels will soar and can stress or kill fish. But even after an aquarium is initially "cycled," it is not unusual to go through mini-cycles from time to time. For that reason, include nitrite testing as part of your monthly testing routine. Any elevation of nitrite levels is a red flag that indicates a problem brewing in the tank. If a fish is ill, or dies, it's wise to test for nitrite to ensure it is not contributing to the problem. The only way to reduce elevated nitrite levels quickly is via water changes.


Although nitrates are not as toxic as ammonia or nitrites, they must be monitored to avoid stressing your fish. Nitrates can also be a source of algae problems. Nitrates will rise over time and can only be eliminated via water changes. Monthly tests are important - particularly when breeding fish, as young fish are more sensitive to nitrates than adult fish. Test monthly and keep levels low to ensure a healthy tank.

Nitrogen Cycle

This cycle usually takes from 2-8 weeks to complete and will happen in all new aquariums. You could speed up the process by using the filter material or gravel from an established tank. Even then it could still take a few weeks for the tank to cycle. This is the cycle during which ammonia is converted to nitrites and nitrites are converted to nitrates.


Aside from new tank syndrome, pH is the most frequent cause of fish stress, which can ultimately lead to fish loss. Unfortunately, it is usually the most overlooked parameter. Fish cannot tolerate sudden changes in pH. Even a change of 0.2 can result in stress or death if it occurs suddenly.

Know the pH of your fish shop's water, as well as your own, so you can be acclimate new fish properly. Keep in mind that if you use tap water, it has dissolved gasses from being under pressure. Let it sit overnight before testing the pH.

pH can, and will, change with time. Fish and plant waste, water evaporation, water addition, and water hardness will all contribute to changes in the pH. As a rule of thumb, pH in an established tank should be tested once a month, and any time there is a fish death or illness.

Another factor of pH is the buffering capability of your water. If your water pH changes suddenly, or drifts regularly over time, you should check the KH (Carbonate Hardness) of the water. Consult your local fish shop for KH testing, and for buffering compounds to stabilize the pH level.

Water Hardness

The hardness level of water is dictated by the amount of minerals dissolved in the water. Calcium and magnesium are the primary minerals in tap water. "Soft" water has relatively few dissolved minerals whereas "hard" water has many dissolved minerals. Water hardness is not really an issue unless your water is excessively soft. Then you may have problems with runaway pH levels. For saltwater aquariums this is especially true. The carbonate hardness of saltwater can give you a good indication of how stable your pH is.


This chemical is found in most tap water and it is used to kill the bad bacteria in our drinking water. Clorine must be eliminated before entering your aquarium or it will kill your tropical fish.


Chloramine is a combination of chlorine and ammonia. It is a stronger disinfectant than chlorine alone and is used in areas where this extra disinfectant is needed. As with chlorine, you must eliminate this chemical from your tap water before adding it to your aquarium or it too will kill your tropical fish.

Other chemistry issues to be aware of include:


This heavy metal can come in with the tap water if you have copper pipes. It can also get introduced to your tank if you've used any copper based medications. Copper can be very harmful to fish and invertebrates.


Whenever anyone complains that they cannot win the battle against algae, phosphates immediately come to mind. Phosphates serve as a nutrient for algae, and elevated levels will certainly add to your algae woes. A leading cause of increased phosphates is dry fish food - particularly overfeeding with lower quality foods that are high in phosphates. If have algae overgrowth, test for phosphates. There are filtering materials available that remove phosphates.


This is the amount of dissolved salts in water and is measured using a hydrometer.