Bad Tankmates

From Microcosm Aquarium Explorer

Bad tankmates

Mary E. Sweeney takes a lighthearted look at which fish make bad tankmates

Marc Weiss, discus raconteur and an old pal took my request very seriously when I asked him what fishes he thought were bad tankmates. I’m taking a big step with my reputation here, but some of these had me giggling too much to type... Is it beneficial to put a Surgeon fish in with the Bloody parrot cichlids? Do not keep a Grasstail guppy with a Grasscutter catfish. Do not keep Stonefish with Glassfish, as he who casts the first Stonefish ... you get the drift. Then, thank heavens, he got a little serious and added the valuable information that I can always trust him to come up with. (I just have to pay the price of hearing the silliness first; still, better to hear silly quips than a sad sap any day of the week).

Combinations to avoid Kissing gouramis peck on the sides of flat fishes like angelfish and discus and will cause their death in a short while. The wounds often mimic a skin disease as you may not see the gourami as it pecks at the other fish. So it is entirely possible to treat for a mystery disease when it was a deadly hickey that was the problem with the fish. Plecos are also notorious for denuding the slime of discus and angelfish. It’s not just Hypostomus, as many think, but the many, many new ‘L” numbered pleco types are unreliable as far as that goes. Of course, having an ample supply of driftwood will sometimes prevent the problem, but at what cost is the experiment proven? Ancistrus, however, have thus far escaped blame in this department and I have yet to witness or hear reports of this behavior toward discus or angels from ancistrus. Mary Bailey, as ever, has lots of good advice: Tiger and Rosy barbs and Black tetras will shred the fins of long-finned fishes. It is not their goal to eat the other fish; they are just delinquents that have to have a go at any available fin. The only things that help reduce this behavior are keeping them in a spacious aquarium and a larger shoal than you would necessarily feel was required. Space and company will keep them out of trouble. No matter how hard you may wish to keep some fishes together, there are many species that will never be acceptable tankmates. The reasons for this are not always the same. In fact, there may be far more reasons for incompatibility than one would imagine, but what will always be true is that some fishes will never get along with some other fishes in the confines of the aquarium environment.

Subtle or outrageous The incompatibility issues are not always obvious, as in the large predator: small prey situation. With some fishes it’s pretty clear they are not going to be able to be kept in the presence of each other no matter how nice you are to them. Sometimes the predator is one generally thought of as a ‘gentle’ and ‘nice’ fish and is often picked upon itself, like discus. There aren’t many fishes that can be kept well with discus unless the tank is very large and the discus very few. Keeping discus with Cardinals and other tetras of similar size is not just a prey thing. Discus will oft time kill the tetras by biting off their little heads in the middle of the night. (Personal conversation, Mary Bailey). It’s always good to study up on new acquisitions instead of simply buying new species and hoping for the best. Unfortunately, it’s not always easy to find out which fishes are good comrades for other species. Many authors are afraid to take a stand because there are always exceptions of one kind or another. Everyone has a tale of two male bettas who got along just fine. Well, everyone who knows bettas knows that male bettas do not get along with each other. Maybe one didn’t swim straight, who knows? Maybe the tank was so huge they never met each other. Also, some female bettas are better looking than others, and just maybe there were really a male and a female in that tank, and finally, there are always exceptions, almost. Then there’s the fact that female bettas always get along, not so. Female bettas can take a dislike to one another, just like any other fish. No, they don’t always get along. Also, male bettas need to be initially watched with other fishes. Sometimes they single out a certain fish or species and decide to hate it. Meanwhile, you can’t ever find another male betta that feels the same way about others of that species. It’s another “go figure it out” moment, and we have many of them in the fish life

Bully fish Aggression and stress will undermine the health of any fish, no matter how large or healthy it was when you placed it in the tank. Even though the aggressive fish may be smaller and not have any chance of eating the fish it’s bullying, the larger, but passive fish will be undone by the daily challenge of living with aggression. A good example of this is the discus with any active, pecky tetra. Bully fish may not challenge the other fishes head-on, but may not allow the others to eat, school, or even have their own territories. Lee Finley, book reviewer of note and long-time catfish expert has this to say to add to our list from his days in the retail trade: “the customer(s) that wanted a nice school of neons and/or cardinals and then one of those active, always swimming, silvery black spotted catfishes with the long barbels, Pimelodis pictus. Pictus and small tetras... a big potential no-no.” Keep fish that are meant to shoal in groups of six or more. Without the companionship of their fellows, they will not look as good as they should and they will slowly fade away to nothing. It’s stressful to be alone when you’re meant to live in a crowd. It’s the old “safety in numbers” thing and these fish really do need to live in numbers. Frontosas don’t do well with other Tanganyikans. Typically, the aquarist buys a small, 6-7cm Frontosa, not realizing how big it is going to get. It’s bad news to mix any longitudinally banded Melanochromis sp. with any other similarly banded fish. The stripe pattern is like a red rag to a bull. Freshwater crabs and freshwater fishes aren’t tankmates; they’re food, one for the other. Yes, they live together in nature, but generally one predates on the other, and in the aquarium there is no escape. The same situation exists in trying to keep freshwater lobsters and shrimp, especially with large cichlids like oscars. An expensive meal for the fish. Turtles are not to be trusted with fishes, especially not the baby softshell type of turtle. The same goes for African clawed frogs, albino or not. They may be cute, but they eat your fish. Don’t keep most non-mbuna Malawi cichlids with mbuna. Aulonocaras are particular victims, also Cryptocara moorii and Dimidiochromis compressiceps, actually are very shy fish.

Fry eaters Killifishes are verboten in tanks where you are trying to breed anything. They are most persistent in hunting fry. Plecos and open-brooding cichlids are not good together. The plecos love to eat the eggs at night. White Clouds (Tanichthys) and anything really tropical are not good tankmates, because the temperature is too high. White Clouds go well with hillstream loaches, which are also sub-tropical. Pike cichlids are bad tankmates for just about any other fish, including a potential mate that is less than 90% of its own size. A number of catfishes will happily consume a fish half their size, or larger. Rams and poeciliid livebearers aren’t good tankmates. Rams don’t thrive in hard alkaline water; livebearers don’t do well in soft acid water. It is impossible to provide for both in one tank. Uaru and plants. They will be happy Uaru and no plants. The ‘Central American cichlid bloodbath’ is well known by experienced hobbyists. They were so cute when they were little. Then they grew up and became gang members. Much like urban sociology, this is the general result of not understanding that if you cram several large cichlids into an area smaller than the territory one of them would hold in the wild, there’s trouble coming. There is so much more to the compatibility discussion, I know I’ve just touched the surface here, but scarce as good information on the subject is in the hobby, I hope I’ve helped save some fishes and will add to the list in future articles. Best fishes.

Sidebar Just for Fun Do not keep Balloon mollies with Needlefish. Do not keep Walking catfish in running water. Do not keep Hatchet fish with Glass fish. Do not keep Stone fish with Glass fish. Do not keep Devil fish with angelfish. Do not keep Wolf fish with Sheepshead minnow. Do not keep Snakeheads with Mickey Mouse platies. Do not keep Lionfish with Tigerfish. Do not keep a Merry Widow livebearer with a Black Widow tetra; the former will get depressed.