I had a 6 inch bristlenose pleco and a betta in a 10 gallon. Before my weekly waterchanges were enough, but recently my pleco's big size has made my water changes more important and so I upgraded to a 20 gallon. My betta is doing fine, but my pleco is sitting in the same spot for hours and won't touch his food. I have never had problems with him not eating. I mean every once in a while he wouldn't eat it, but I'd leave it during the day and it would be gone. I'm really worried so I look at other forums and I saw things about others and ammonia, which is a possibility with my tank I didn't do a full cycle because I dont have room to run the old tank while I cycle the new one. I did use about three bottles of tetra safe start. One i used right away and I saw as I was throwing it away I saw it was old so I put a newer one in and bought one. Then I just put one in now because if the ammonia level. My ammonia level is .5-1.0 I use the strips and it was invetween there.