So-called Community Tanks

By Frank G Anderson

I use the phrase so-called to get your attention, because the community tank has been accepted by many thousands of hobbyists as being a tank where all the fish get along together and they can all be fed without much ado, generally. In practice, nothing could be further from the truth. The so-called community tank must be populated with fish that can tolerate the same water conditions, but which also can tolerate one another under a wide variety of conditions. Resorting to the Internet/Web to double check on this doesn’t always produce tangible results. Yahoo, when asked to search for fish, community tank, gave me 16 sites. Infoseek on the other hand, provided over 1.6 million. Trying community tank gives all sorts of strange references, most of them having little to do with fish. You might want to check FINS at http://www.actwin.com/fish/index.cgi or Fish at http://www.actwin.com/WWWVL-Fish.html . This second site is interesting in that it has an angler section (in case your fish interests are also outside the aquarium), but there is an ichthyology and hobby section that are very helpful to beginners and intermediate hobbyists who want to find out more. You might also want to check out the CAN (Aquatic Conservation Network) at http://www.achilles.net/holiday/acn/acnhome.html .

The electronic lost-in-the-woods is similar to the same kind of loss-in-the-woods that the average home aquarist faces when keeping fish. He or she wants a wide selection of colorful, active, interesting, and healthy fish that not only enjoy their environment, but enjoy it so much that they will successfully breed. In the meanwhile, these fish must remain healthy, relatively stress-free, and live with one another until the point of procreation. This is the so-called community tank, then, a single aquarium that houses various fish species that do not harm one another, and which get along in the same general water conditions.

The community tank stops being a community tank too quickly for many of us. Sometimes it’s the fault of the retailer we bought new fish from. We were sold Convict cichlids, told that they will get along with other fish species. And we find out quickly that not only is that not true, but they are very aggressive toward one another. Not all retailers are knowledgeable about compatibility, just as this writer is not. I can not recite every species and tell you whether it will work in a community aquarium, but what I can do is to lay down some general guidelines if you are considering a community tank, or if you all ready have one and things just are not going very well as far as community spirit goes.

One important aspect of fish keeping, which really develops later in the hobby but which should be mentioned first, I believe, is that tropical fish that are sold as community fish are of two types: egg-layers and live-bearers. Why is this important to mention at the beginning? Because not only do mating rituals vary with species to species, but the fact of new eggs or live babies into the community tank will have an impact on just how much fish remain community-oriented. Little eggs might be delicious to gouramis, for example, and they can easily interfere even with angelfish to eat eggs or the very young fry that hatch from deposited eggs. Too, live-bearers like swordtails and guppies can eat their own young (as do many fish species), and the young need a place to remain safe until the danger period is over. This is usually how long it takes for the baby fish to grow large enough so that it is no longer considered easy eating. The subject of compatibility came to me today via E-mail. A reader asked how I felt about combining his favorite fish, the ram, or Butterfly cichlid, with discus. The reader really wanted to put the two together, and my first reaction, always favoring keeping discus by themselves, was to advise (which I did) that the two should not be kept in the same aquarium. There was another reason, however, which precluded the combination even more, and which is an extremely important consideration for any fish species combination - water temperature. Discus do not do well below 83-84F, while rams find comfort in the 73-78F range, considerably below that of discus. So, when you consider compatibility, consider water temperature(other water characteristics can be vital, and will be mentioned below). Fine, you say, but where do I get all that information? The Internet is one easy access to it, but being a book person, I prefer to have several references on hand to guide me along, whether it’s to check on what I just said, or to plan ahead for more fish tanks, or to analyze a problem I have and wish to resolve. Here it’s best to check the copyright date and date of printing, as many aquarium books that are over 6-10 years old, as helpful as they may be, often contain dated information that has been changed. Fish species may have been renamed, and certainly information on feeding, prepared foods, breeding and other aspects of the hobby has been updated and improved upon. If you are going to buy a book, get one with pictures, yes, but also with good narrative, possibly accompanied by brief descriptive sections that include information on the species name, sex characteristics, water conditions, breeding behavior, feeding requirements, etc. Always check the author’s credentials before buying the book. Dick Mills, among many others, is a fine and highly respected writer in the field.

More on water conditions. A reader of Tropical Fish Hobbyist (TFH) wrote to the editor complaining about a problem he had with his tank crashing, or the pH dropping to very low values and ammonia and nitrates climbing way up after a couple of months. I once had this problem, and discovered, by logic, that in my case at least, the problem was caused by gradual build-up of sediments which produced these toxins, in the gravel. I was then, and still favor, keeping tanks with undergravel filters for community fish, and like the reader mentioned, kept changing water (the usual 25% every week), to find that after a while, it just didn’t matter. So one day, I said to myself, let’s clean out the gravel, really get rid of whatever might be in it, and that should do the trick. While it did do the trick as I thought it would, I was still surprised, as you will be, the first time you really clean out your gravel. Many hobbyists might not even know that this is a requirement for undergravel filter systems, and more so for tanks with decorative gravel without the filtration aspects. Sediment becomes accumulated in the gravel, where it builds up toxicity that is eventually released into the water and which quickly affects fish behavior and health. So, clean your gravel! How?

Gravel cleaning is done best with a simple siphon found at your neighborhood fish shop/pet store. It consists of two pieces of clear plastic, one a clear PVC tube about 4 inches in diameter, connected to the second tube, a clear flexible plastic tube about 1" in diameter. The trick is to stick the larger end into your gravel, and gently swirl/lift and jab this into the gravel to loosen the sediment trapped there. While you are doing this, you also would have had to create a suction on the other end, siphoning the water out of the tank through the tubes. Since you don’t want water going into your living room, or probably don’t have a bucket large enough to catch all this water, why not connect a garden or other hose onto the end of the 1" diameter end, and go outside and create a vacuum on the further end of the hose, where the tank water will then be drawn to from the tank? I have done this and continue to do so. It allows me to place the aquarium waste water anywhere I want. Keep in mind the head, or vertical distance from the point in your tank that you are jabbing the siphon to the lowest point outside where the hose is draining water to. The more this distance, the greater the suction. If the distance is over 4-6 feet, you might find that you have emptied your 20 gallon tank in about a minute, and not have plenty of dried fish! You can also restrict the water outflow by directly squeezing the hose to make it narrower in diameter, or placing some type of valve in-line. This is a trial-and-error operation. You also have to get used to just how far you can and should jab the larger clear PVC into your gravel, since you do not want to suck gravel out the hose and into the ground.

Probably as important to overall water conditions as temperature is, pH or just how alkaline or acidic your water is, will have a large effect on fish health, and their ability or willingness to breed. Tap water comes out of taps across the world anywhere from 5-8, more or less, with 7 being neutral (neither acidic nor alkaline). When you buy fish that require a pH in the slightly acidic range, this precludes combining them in the community aquarium with fish that need slightly alkaline water. The pH values for the fish are too far apart for them to remain comfortable, and sometimes, for them to remain alive. In addition to selecting fish for a community tank that can tolerate the same/nearly identical water conditions, the hobbyist must also learn how to regular or alter pH if the need arises. Being partial to the natural cycle, I prefer not to use artificial pH uppers and downers, but recognize that today there are several types of water buffers and pH adjustment aids that will get the job done without harming your fish. If you do have a pH problem as did the reader mentioned earlier, you can drop me a line directly at (E-mail: tongmuan@loxinfo.co.th ), or take one of several steps to alter the water pH. Besides the uppers and downers and buffers mentioned, simple water changes often work to bring pH up or down, depending on the pH of the water being used. In making water changes, be careful to try to use water that has had its chlorine dissipated, either by standing for 24 hours, or having a chemical dechlorinator added.

Temperature, pH,…hmmmm…. What else is there? Ah yes, of course, hardness. Hardness gets mixed up with pH from time to time (made that mistake years ago myself), but it is a different value. Hardness in the aquarium is measured in terms of total hardness or carbonate hardness. I measure both values to ensure they are in line with the requirements of the fish. When water hardness is too high, it is easily decreased by placing a water softener in-line to your fish tank, or by running tap water/conditioned water through a water softener and then using this as your new water each time you make a water change.

Finally, a brief note on water changes. I have often incredulously heard people say that they changed their water and still have problems with fish getting sick or dying. Incredulously? Yes, because when I asked them how much of a change they made (assuming that it was too little), they occasionally told me all of it!). Don’t ever, ever make a 100% water change. Not unless someone put poison into your tank and you are faced with an immediate life or death situation for your fish. A 100% water change basically alters all of the water characteristics your fish have become used to or are trying to become used to, and can easily kill them immediately if not sooner. The standard water change recommendation for most freshwater aquariums is generally accepted to be weekly, and about 25%. Now there is a lot of latitude here, depending on what fish species you keep, water conditions, your maintenance schedule of your aquariums, feeding, plants, etc., etc. But certainly no less than 25% a week. This change can be made together with your siphoning of the gravel.

I hope that the above has provided some insight, and would certainly enjoy hearing from anyone regarding the column or any challenges they face and haven’t had anyone they have gone to to date help them sufficiently. Insight is an important aspect of this hobby.