My Rainbow Shark is a very odd fish. He killed a younger rainbow shark when I first got him and he attempted to kill a Bala Shark by eating almost it's entire dorsal fin off. My guy seems to only pick on fish that will run from him, I guess he's a fan of the chase..lol. The oddest behavior I have seen from him is that, when 3 Dwarf Gourami's were introduced to his solitary tank, he immediately changed his natural behaviors to act like a Gourami, he flipped his body at the gourami's like they do to each other, started eating from my finger like they do, and other such things. Then I introduced Clown Loaches to the tank and he immediately changed behaviors to hide with them in the pinapple ornament, sleep with them, and following them everywhere. I've also noticed that, when stressed, his normally black looking body will turn a very light green, this is most noticable if I chase him with the net, but I try not to very often...lol. He's a cute little guy. :)
I have had a redfin shark for over 2 years now in a 175 liter aquarium. The only other fish in the aquarium are tiger barbs. The aquarium is well planted, with a soft substrate and plenty of driftwood hiding places. My redfin spends about half of her time in the driftwood and the other half split between chasing the tiger barbs and cleaning the algae off of the plants and the glass on the tank. She has grown to be just just over 13 cm, with deep orange fins and tale, while her body is a soft, muted black. I have never fed her anything other than flake food. She seems more interested in cleaning off the plants and the aquarium glass than eating the flake food. I tried putting a male in the aquarium about a year ago, but as others have pointed out, they are territorial and they did not get along well at all, even with equal amounts of driftwood and hiding places at opposite ends of the aquarium she relentlessly chased and badgered him until I returned him to the pet store. Maybe in a larger aquarium more than one would not be so bad, but once one has laid out a territory any new redfins don't have much of a chance. Overall they are very pleasant fish to watch as they swim very gracefully and glide along the aquarium plants in search of algae.
This shark is quite a good community tank fish when he is put in the right environment. I've owned about six of them over the course of many years, and usually I have two at once. First you mustn't try and jam them in too small of a tank. They are very lively (when happy) and this energy when confined turns into aggression. Even one shark in a small tank can be bad, I recommend a 200 liter. I have kept an albino and a regular rainbow in a 200 L along side numerous loaches (clown, Burmese, Pakistani, and Kuhli). Also in the presence of baby angels, kribs, rams, every common gourami, male and female bettas, iridescent sharks, silver dollars and several smaller tetras. Basically, give them enough space/hiding spots and food, and they are extremely friendly. I wouldn't put it past them to give a small, lower level fish like a bumble bee gobie a hard time, but when mixing sizes that are that extreme you have to be careful anyway. So when acquiring this energetic bottom feeder, be careful, they have a lot of energy that can either go into cleaning your tank, or terrorizing your other fish. In general I don't think fish in excess of 10 cm should be kept in tanks maller than a 160 liter for a prolonged period of time, because this lack of room seems to effect the fish's overall happiness, and in the end it's overall well being.
I own 3 rainbow sharks and four if you count my albino. What I suggest is that you do not get a rainbow shark if you let it settle and find territory, then get a new one to live with the first one. They will more then likely fight. If you plan on getting more than one, make sure that they are very close in size and that you buy them at the same time, so that they establish their territory (you may want to have some caves).
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