Plecos not doing well... can't figure out why!

[Bristlenose 94]

So, a while back my clown plec in my 38gal stopped eating and got really skinny. I moved him to my 10gal setup and he got well again, then moved him back to the 38 and he got skinny again. So he's staying in the 10.
I also had a BN in the 38 who was doing very well while the clown was going through all this. I never saw them interact and the BN was female so i doubt territoriality was the issue. Anyway, the BN was eating and stuff but she died while I was away at school last month (my family doesnt do water changes), so i did some water changes over the couple weeks I've been back and got a new one.
Now THIS BN won't eat and is getting skinny. He is also staying in the upper 1/3 of the tank almost all the time, barely moving. Ive probably changed 80% of my water while i've had him, and he hasn't made much improvement other than recovering from some fin rot he had in the store. This leads me to believe it isn't the water parameters causing these problems.
I moved the BN to my 10 gallon planted setup with the clown for now, where he's sitting on the gravel.

So, i really have no clue what's wrong with my 38 that's causing plecos to stop eating and stuff. Every other fish in it (8 various tetras, a couple gouramis, a festivum, and a Chrysichthys cf. nigrodigitatus cat) is completely fine, acting normal, and eating. There's an ac110 filter on the setup and it's very broken up by plants and decor to keep nipping/chasing at a minimum.

Anyone got any ideas?

[Birger]

a couple gouramis, a festivum, and a Chrysichthys cf. nigrodigitatus cat) is completely fine,

You have some fish in this tank that they may be having trouble competing with for food and space, would not surprise me that the Chrysichthys may possibly claim the tank for itself especially at night.

What are you specifically feeding the plecos?

Birger

[Barbie]

At the top of this forum there is a sticky topic. Could you please copy and paste and answer all of the questions in it? That will give us a much better chance of actually getting you a worthwhile answer. Otherwise we're just shooting at trying to find the right question for the information we need. If you start out with all of those answers, it will narrow down the refinements needed . Thanks!

Barbie

[Bristlenose 94]

1. Water parameters
a) Temperature range. - 79-81 F
b) pH. - 6.0 (possibly less, my test kit only goes down to 6.0)
c) GH. - Not sure
d) KH - Not sure
e)Ammonia, Nitrate, Nitrite, levels. - Unsure, probably minimal because I have an established setup, tons of plants, large filter, and nothing's died recently
f) Water change frequency - It changes, I've been doing a 35% change every weekend that I've been home from school and a 35% change weekly during this break im on now.
(Most LFS's will check your water and give a list of readings).

2. Tank set up
a) Size. - 38 gallons, 36"x12"x20"
b) Substrate. - gravel
c) Filtration. - ac110, 500gph
d) Furnishings. - bogwood, mopani, plants
e) Other tank mates. as mentioned before, a festivum, gouramis, the chrisichthys cat, several tetras. All still juvenile.
f) How long has it been set-up? 5 years now.
g) When was the last new fish added? About 10 days ago.
h) Foods used and frequency? Flakes once or twice daily (in the morning and/or at night), one or two algae wafers at night. Occasional frozen peas or fresh cucumber.

3. Symptoms / Problem description
Fish not eating
4. Action taken (if any)
None yet other than water changes, which havent been done in a month
5. Medications used (if any)
None

I'm thinking it might be the pH since it's likely below 6... I've watched the tank at night and the Chrysichthys doesn't really bother the other fish, just kinda swims around and does his thing. I haven't fed veggies since I've been home though so those might be worth a shot as well.