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Hey guys, a friend called me the other day, she had a "killer plec" she said....

I went to her house and found a 10 gallon tank with poor filtering and an injured fish. The killer plec had already wiped out two other fish and this was its next victim...

I took the Plec home and have had no problems since. I told her I believed it was attacking fish out of hunger, competition for food was stiff in this tank.

I inmediately told her she was overstocked, which she finds hard to beleive because they guy that set up her tank told her she could have up to 15 fish in this tank. I told her 15 small tetras yeah but not the kind of fish she had in there.

All oriental fish (goldfish family) one of them, the body alone was the size of a tennis ball, perhaps a tad more. Several other smaller goldfish (about 3) and this plec, about 4-5 inches long.

I thought I would post this on here so she could see your opinons on the tank, I told her, just the tennis ball fish puts you overstocked in this tank. I would like to hear your opinions on this subject, the injured fish seems to be doing better, we'll have to wait and see for a few days and the plec is a peaceful little guy if fed properly. Then again most plecs are territorial but not downright killers.

I appreciate any and all comments for her.

10 gallon tank may be used as a growout tank or a quarantine tank for goldfish, but is by no means a permanent household. Same goes for what I assume to be a common pleco.

In such a set-up I am not even sure that the water would be appropriate. If pH, ammonia, nitrites, and nitrates were tested I wouldn't be surprised if something were out of whack. The presence of ammonia and nitrites are a more likely killer of the fish than the pleco.

A killer plec is nigh impossible. Plecs are known to attack other plecs in territorial disputes; though these scuffles can actually lead to death, they usually won't behave this way to other unrelated fish. However, plecs are opporunistic feeders and will feed on bodies that are near or already dead. A common plec of that size in a 10 gallon should be moved out as it has no space to continue to grow; as a very messy fish, it should hardly be kept with other fish as messy as goldfish in a 10 gallon. Plecs should be fed their own food, of course; algae wafers are eaten with gusto, but as digestive machines they'll put out an equal amount of waste products back into the tank.

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The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.

Goldfish alone are very messy fish. Infant fancy goldfish can usualy be kept to a rule of 10 gallons per fish for example you could house 5 3 inch fancy goldfish (ranchus, orandas, fantails etc) in a 55 gallon. However goldfish grow drasticaly! You say the size of a tenis ball ive seen basketballs .

Idealy for adult goldfish 6 inch+ it is recomended you should have 30 gallons for the first goldfish then an aditional 10 for the next so for all you accomodate 5 infants in the 55 you could only get 3 adults in the 55.

On top of the tank size you also need 10x or above GPH on the filter which more than less times means an external filter.

This is because of the amount of waste that the goldfish produce they produce more waste than just about any other fish. They produce strong harmful toxins just from breathing. They also poop like crazy you wouldnt believe the size of some of them (ew gross).

Something I would recomend for goldfish is a UV steriliser of some kind because they dont allways hav the best immune system this is because of the mass breeding and cross breeding to get new traits or larger wens, longer tails, purerer pearlscales etc. Also sometiems goldfish are kept in substandard conditions in pet shops and carry diseases to their new homes.

From the sounds of things she will need a much bigger tank and because she has the big one and the other 3. So fully grown she would need a 70 gallon tank, a 75 would be better as it would leave some breathing space as well which allows for decoration and gravel.

As for the pleco, common plecs are a no no with goldfish as they have been known to try and sometimes actually manage to suck the slime coat of goldfish because of how slow they are.

There are some fish that are compatable with goldfish as long as you keep an eye out. The most common tank mate for goldfish are dojo loaches or weather loaches prefaring cooler water and a heavy waste creater its self, they need to be kept in pairs at least or trios preferably.

There are also a few plecs that are good tank mates for goldfish and these are the rubberlips and bristlenose plecs. They nearly allways stay vegan all their life dont out grow tanks and are peaceful algae eaters.

I think the best thing she can do is either rehome the fish asap and get small tropicals OR get a 55 gallon tank a big filter cycle it and get choose three of her favs in that tank and then maybe a BN or rubber lip to help clean the bottom a bit.

Hope ive helped and if Ive said anything that is wrong can some one please tell me and i will edit acordingly i would hate to give bad advice.

Killer plecs are a reality. Its rare, and it usually happens only during overstocking, but it does happen. Other mitigating factors like a lack of adequate nutrition can force a plec to browse on fish during the night ala chinese algae eater. Some can be brusque and a big plec in a 10 gallon knows what it must do to survive. Simply by scraping other fish, ramming,being brusque, and attempting to dominate food resources.

They are survivors , they will do what it takes to survive in overcrowded conditions even if that means unintentionally destroying other fish. This is not the direct elimination that cichlids etc will practice, but the effect is much the same even if it takes much longer.

Besides its always the fault of the keeper. Its a no brainer that plecs shouldnt be kept in small overcrowded tanks, or with two many conspecifics.

Its not that they can't kill, its that they normally dont, and that is based on conditions , not their ability. Cater for them properly and there should be no problems.

Ive had plecs that fought when they grew to a size they needed seperating from each other. The fighting was a great deal more violent and repetitive than most people who havent seen it would believe, and their territoriality can be ounced. I did seperate mine, but if you dont, then... well the consequences can be severe. The same goes with overcrowding them generally.

Plecs are peaceable but not completely harmless. People forget there is a difference between the two. The latter means they must be catered for properly.

Fish turning to fighting in suboptimal conditions is not unusual, some species are even capable of monitoring levels of urine and hormones in the water to give them a clue as to how much of a population is near them. Sometimes therefore the water pollutant level alone can make them aggressive.

I'm tryings advice was pretty good. Those fish should be seperated into tropical and coldwater and given much bigger tanks and filtration. Whether the fish shop or your friend does this matters not, but it will have to happen, and soon. Like yesterday. Your friend has been lethally misinformed by the usual motley crew at her LFS.