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dazeek 01-03-2011 05:29 PM

My pleco is eating my fish??
Is it normal for a common spotted pleco to eat other fish? I recently got 6 cherry barbs and they keep disappearing. I just caught my place eating the last one so I am assuming he ate the other five as well. Help?!

dazeek 01-03-2011 06:15 PM

I have a 150 gal fresh water tank with the following fish:

1 pleco
1 striped cat fish (last i knew - you never see him)
3 phantom tetras
1 tiger barb
2 danios
4 aust rainbows
1 turq rainbow
6 gold barbs
2 rummy nose tetras
1 mickey mouse platys
2 chinese algae eaters
1 balloon molly
5 serpae tetras
2 black&red platy type fish (forget their species name)

I also had 1 turq rainbow fish pass away 2 days ago and 6 cherry barbs disappear within the past two days - i caught the pleco eating one.

My water is at

7.6 ph (it's always right around that)
0 ammonia
0 nitrite
80 ppm nitrate

I have had the tank running smoothly for over 6 months. The turq rainbow I had for about 3 months and the 6 cherry barbs for about 2 weeks. We did a 50% water change on new years eve.

Any clue whats going???? My nitrates are running higher than they usually are and I do shake the bottle for 2 mins and tested it three times this time

Byron 01-03-2011 07:04 PM

While pleco are often territorial with their own species, or sometimes other substrate fish, they rarely attack upper fish. It is however quite possible that the cherry barbs died (or were somehow severely weakened to the point of being on the substrate near death) and the pleco will then readily eat the corpse.

As the barbs were recent additions, there is probably a reason for their demise. To ascertain the issue with the barbs: what size tank, what fish are in it, what are the water conditions (ammonia, nitrite, nitrate; pH).


cbirk 01-03-2011 08:42 PM

in my experience plecos will only eat fish other fish if they are already dead and laying on the bottom of the tank. Did you happen to do a water test when you introduced the new fish? if it was already high perhaps it was too much for them. I would also suggest when you put more fish in, to place more tiger barbs in the tank. if you want a variety they come in albino, cherry, green and black. But they will be happier for it.

I have 4 serpae tetras, and they can be pretty aggressive, so they might be the culprates behind the cherry barb disappearance. I have heard story's of those two species before, however I have cherry barbs in my tank with them too and have never had a problem.

Either way you defeinately want to get that nitrate down with water changes every day. Not more than 50% though. I would also look into your tetras and mollys, I would imagine they do better in groups of at least 5 as well. Your tank is prtty good size so I dont THINK your over stocked, but I always add an HOB filter to my big tanks plus a canister filter thats rated for your tank size.

1077 01-04-2011 01:52 AM

Nitrate readings are indication of over feeding and or infrequent water changes. Ideally, you want Nitrates around 20 to 40 ppm which can be achieved by weekly water change of 30 to 50 percent and once a day feedings.
As for the Barbs, I agree with Byron ,,Plecos do not normally attack fish especially fishes that are much quicker such as the barbs but they will eat remains of dead fish or sick dying fish.
A couple things could be happening in my view. The lone Tiger barb could be inflicting damage to the fishes for they are notorius fin nippers ,and should be kept in groups of nine or more to help keep the fin nipping to a minimum and largely amongst themselves.Fin nipping causes stress to the victim and over time,the fish succumbs (dies) due to stress and or bacterial infections or fungus that take hold at the damaged areas.
Could also be that Chinese Algae eaters are doing what they do best, Harrasing the other fishes to the point where the fish becomes stressed and weakened. They are poor tankmates for most community aquariums, they are poor algae eaters,and will as mentioned harrass other fishes as they continue to grow.
and lastly,, It is entirely possible that the barbs were sick when purchased. sometimes takes a week or two for sick fishes to present symptoms and usually by this time,,it's too late for help and the fish die.
You can help prevent other fishes from becoming sick by selecting healthy looking fish,quarantining new fishes for a couple weeks, and by acclimating new fishes slowly to your tank as opposed to just floating the bag for a while and then dumping the fish in the tank.
Not saying this is what you have done ,just offering some possibilities.

Byron 01-04-2011 12:38 PM

Yes, I concur with 1077, and will expand on a couple things that stand out to me from your info.

When new fish are introduced to any tank, they are under severe stress--from their initial transport to the store, being kept in what are almost certainly poor conditions in any store, then being chased and bagged, then undergoing a (usual) major change in water quality from bag to tank. Stress weakens the immune system in fish just as it does in humans, making them even more susceptible to any even "minor" issue in the tank. The stress caused to many fish by the presence of fish like Tiger Barb [which send out aggressive signals chemically even if not physically] can have an impact. All of this can play into things.

You have the space in a 125g, so if you like the Tiger Barb, get at least 12 (in total) of them; the info in our profile explains this. [You can click on the shaded name to see that fish's profile.]

The Serpae Tetra is very similar to Tigers in their behaviour. Please read the profile. Increasing the group to 8+ may (or may not) resolve these issues. And btw, while the fish may appear OK now, as they settle and mature their natural instincts may become more pronounced--not always, but often, so it is best to recognize what is likely and be prepared.

Forget rummy nose tetra. They need a large group too, 12+, as noted in our profile of the Brilliant Rummy Nose Tetra [the most commonly-available species now]. But these will be wild caught fish, and in anything but soft (very soft) acidic water, they will not last. They will also be stressed by the aggressiveness of Tigers and Serpae; I personally would never mix these, the rummys are too beautiful and wonderful a fish for this.

Other tetra and danio--all are shoaling fish, requiring a group of at least six but with space more is better. Shoaling fish need their companions to reduce stress, and many have interactive social traits within the group.

I would consider removing the Chinese Algae Eaters. When young they eat algae, but as they mature they eat less and less and almost always attack other fish. They attain 6 inches, so they are a force to be reckoned with and can cause havoc to the shoaling tetra, etc.


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