Red spot on bottom of BN Pleco

[joeyg2100]

This spot showed up today, or it is just the first time I have seen it. It's a 55 gallon Tank that has a sand bottom and water test read. I just put the fish in there 3 days ago. The tank has been up and running for about a 1-1/2 months. The tank is cycled and I have been putting in a few fish every 2 weeks
His other tank mates are Congo tetras, don't think they are the culprits as it is on the BN bottom

PH 7.5
Ammonia 0
Nitrites 0.25
Nitrates 10

I did a 25% WC in case.

 

[joeyg2100]

Well I just went and checked on this fish and it was swimming around crazy and then fall to the bottom. I ended up taking it out and put it in the QT tank. Probably will not make it through the night

 

[fishorama]

Well, it doesn't look good, I'm sorry. Red can be a sign of bacteria or some internal parasites. I'm also sorry I can't offer good advice. It looks like the cloaca (opening/vent) is kinda large, I have no idea what that might mean.
Does it poop normally? Can you see any red strings protruding from the vent at any time (but not necessarily all the time)? My best guess is either cammalanus worms (my best guess right now) or bacterial infection. Watch your other fish very carefully, especially near the vent, they may already be infected (all too likely)...Are all the tetras acting normal? Eating well? Redness?
Quarantine needs to be before you add fish to your tank, I do it for a month or more. Do NOT add any new fish until you see (for several weeks) that all your fish are healthy (not just that you "hope so"). In the mean time research treatments & their availability locally or online

 

[joeyg2100]

Okay fish has died. Here are some closer pictures. Seems to be just blood around the area. No worms from what I could see. Can't seem to find anything on common fish diseases. Let me know what you all think. All other fish seem to be acting fine for now