Reptile & Amphibian Forums

I have had a 20-gallon tank for about 10 months now. Last week, I got a golden albino bristle-nosed pleco to help keep the algae in my tank in check (which he has done very well at). However, in that same time span, five of my eight cardinal tetras have wound up dead and stuck on the filter intake. I have checked the water and my pH is between 6.6 and 6.8, my hardness is low, and my nitrate and nitrite levels are low. I must also mention that I have three Glofish, a medium-sized glowlight tetra, and a head and tail light tetra (one I've had since I got the tank, actually).
I wouldn't think a pleco would attack my other fish, but I'm at a loss as to any other possibility.

Does anyone have any thoughts?

What are the ammonia levels? You didn't say, and that could be a possibility. When was your last water change, and how much do you change each time? Your tank isn't overstocked, if you ask me, so that rules that out. Your pleco's temperment is peaceful, so I doubt it is a bully. However, plecos tend to be noctural (at least in general - I don't know specifics on individual species) so perhaps take a peak at your tank at night see if you observe any bully tendencies.
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Phishie
Site Coordinator

"An ounce of prevention is worth a pound of cure."

My ammonia levels are good, too, and I change 25% of the water every 7 to 10 days.