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I keep losing my Chubby plecos for no obvious reason, they're juveniles (4") and in a 40breeder on my central system. The tank is bare bottom with a couple pieces of aged driftwood and some PVC. The only tank mate is a single Kobia guianensis. I've been feeding them like all my other plecos, spectrum cichlid pellets, southern delight community pellets, zucchini (which they never seem to eat), and Sera algae wafers. They don't appear emaciated and show no signs of trama. The system currently has 5 adult common plecos that seem to be thriving in the sump. Any ideas what could be causing the deaths? I started with four but now I'm down to one.

What are water parameters (see sticky: pH, temp, etc)?

My guess is that the bare bottom is not helping.

Ph is 7.5
Ammonia 0
Nitrite 0
Nitrate is around 20 ppm
Temperature is 75f
And now that I look at them they do look a little emaciated? What are they supposed be eating? I try to offer a varied diet yet I've honestly never seen them eat, and I originally got them back at Catcon.

Would it be a bad idea to move it to a tank off the system where I have some other plecos thriving?

Hi all,
You can't really tell, but with rheophilic fish and symptom less death I would always suspect low oxygen levels.

We had a similar "Chubby pleco" (

Parancistrus aurantiacus

) thread a while ago <http://www.planetcatfish.com/forum/view ... hp?t=39885>.

The difference between dissolved oxygen and all the other parameters is that you only need a very, very short period of low dissolved oxygen to kill your fish.

If you have a "wet and dry" trickle filter to your sump? low oxygen levels are more unlikely.

The Common Plecs (

Pterygoplichthys pardalis

) differ from a lot of the more "difficult to keep" Plecs, because they have the ability to extract oxygen via air gulping and a modified gut (like a

Corydoras

can), and presumably inherited from their common ancestor. Rheophilic Loricariids, although they have lost the ability to absorb atmospheric oxygen, will still come to the surface at times of low oxygen.

If you don't have any plants, or a substrate, you are reliant on the microbiological filtration in your filter system for biological filtration. Although your test kits read no ammonia or nitrite, that doesn't mean that there hasn't been some present which has been already converted to nitrate. Again nitrate test kits are unreliable, mainly due to interference from other anions.

You can't easily measure parameters like dissolved oxygen or Biochemical Oxygen Demand (BOD) (I'd actually argue it is quite difficult to measure any of the parameters (other than conductivity) we are interested in without access to an analytical water testing lab. and a lot of time), but you can take steps to maximise dissolved oxygen and minimise BOD, which largely circumvents the need for water testing.

I'm not against water testing, quite the opposite in fact, but the problem comes with the accuracy of the test kits.

cheers Darrel