Blakekr:

Late so maybe I am misreading.

What size tank. Pleco is pretty large (or gets to be)

That said, what is the ph of the tank... most not all tetras prefer lower ph... below 7... (what was in the bag your brought them home in) I do many hours slow dribble to move the ph from store (5) to mine 7.6. Now note I said tetres like lower ph. The ones I got and put into already cycled tank.. are pristella tetras and from my research are hardier and can handle higher ph and even brakish water then most tetras.

Should be no ammonia which means all is off in tank ie not best water. Tetras tend to be very sensitive to water conditions in my experience and research (again prestellas are often used to cycle - something I think no fish should be used strictly for) much hardier.

That said, not fish will do well with not best water conditions.

I would not put any pleco large or otherwise with any small fish. In spite of what you may or may not have read, mine (gone now gave away) would eat my smaller fish including cat fish (pregnant and really upset me, one of pair I was going to breed) you say large, so again what size tank... they could be getting stressed. They also get stressed when not in proper sized school.

Please write again or email me sherryazure@yaoo.com (not getting emails anymore and can't seem to correct) for info on tank size.

Are you over zeolous in cleaning vacumming thereby causing ammonia (bacteria has to start recylce all over again)... Please mentions size of tank so one can determine amount of water changes.... don't do all of gravel all at once. Unless you have live plants you don't need deep gravel..

I would wait to add anything until this is figured out.

Need tank size.

Temperature

PH

Type of filtrations

and actualy size of pleco for tank size.. they grow up to 12 inches and you need a huge tank eventually.

Live plants, any plants, wood for pleco... algae waefers fed to pleco...

The more informatin the better.

Any symptoms with re to fish prior to dying?

Again, though you mention ammonia. zero. Fish have gills that have delicate little arches. This is the area where oxygen transportation occurs. when this is damages (ie fish jumps, they collaspe) or ammnoia or other neg water (ammonia burns this area like acid to them) they then can't breathe and blood gets damaged so on.. breathing hard and lying on side is an indication of this.

Please post more info. Best Sherry