Q. I have a 29-gallon tank that has been running for about nine months. This is my first tank, so I am probably over-stretching the tank's limits, but I do want to have a wide variety of fish and plants. The tank currently contains two raphael catfish, one plecostomus, four sunburst gouramis, one giant gourami, four serpae tetras, three bleeding heart tetras, five cardinal tetras, five marble hatchetfish, three kribensis, one festivum, one flying fox, two tricolor sharks, four coolie loaches and two gold loaches. There are calcium deposits on the hood of the tank and on the glass cover over the lights. Also, it does not seem as though the plants are growing. I would like to know if my tank is overloaded or if I need more fish. How do I judge overcrowding in a tank?
A. I feel that your tank is seriously overloaded. In fact, you could probably populate three attractive 29-gallon tanks with the fish you have. For example, you could place the raphael cats, the plecostomus, the festivum (plus another one of the opposite sex) into one tank, the tetras, hatchetfish and the kribensis in another, and the rest in a third tank.
There is an old rule of thumb that gives a very basic guideline that might help you until you gain more experience: "one inch of fish per gallon of water." In theory, using modern technology, it would be possible to exceed this guideline and add more fish. In reality, however, it is best to be conservative in this regard. Keep in mind that this "inch-per-gallon" guideline is for small, slim tropical fish — larger, deep-bodied fish require more water per inch of length. Also, be aware that this guideline refers to the adult size of the fish, not the size of the fish at the time of purchase. Stores generally stock very young, small fish, which keeps prices low.
I would like to suggest that you invest in a good aquarium book that describes the size and temperament of various tropical fish. That way, you can determine the suitability of the fish you want before you bring them home.
You mention calcium deposits on your hood and light fixture. This can be due to hard water from your water source (talk to your dealer about ways to handle this) or it may be due to the quantity of fish wastes in the water from the high biological load in the tank. The only long-term effective way to counter the high load is to reduce it by removing enough fish from the tank. You could try to lessen the effects of the biological load by doing frequent partial water changes and practicing excellent aquarium maintenance techniques, but this requires continual work on your part. It is much easier to set the tank up properly and keep the fish load down. This also makes the hobby more fun and less work.