What's killing my BN's? Internal Parasites?

[WolfFisho1]

I had about 6 albino bristlenose plecostomus in a bare bottom 55gal they were 1-2in, and a few months old. I had them cleaning up uneaten food that my 10 angel breeders missed. I fed them green zucchini, yellow zucchini, and cucumber about every other day, exactly what all of my other BN's in other tanks were eating, and they slowly died off until only two were left, and one of them just died yesterday. Their stomachs are always full, even if I fast them for a week, and the stuff inside is visibly gray from the outside, which is why I think it might be internal parasites. I attached a picture of the dead one from yesterday.

I treated with one dose of metronidazole when there were still 4 left, but I suppose that was ineffective.

Sorry I did not keep the dead one though so I can't dissect it now, but if I don't get help I'll probably lose this last one within a week.

 

[Lupin]

The metronidazole cannot kill possible nematodes and cestodes. If it were flagellates, that would have been more effective.

I think you need to cut open their abdominal area if any pleco dies (hopefully not with the remaining survivors although the previous ones would have been useful) and find out what was causing the issue. If you are squeamish about it, you might not be able to know what parasites are involved which could give you a chance to save your other plecos. This is your one way to be a step ahead of the possible issue.

You might need Jungle Anti-Parasite Medicated Food here if your plecos are still eating. Follow the instructions as directed. You can buy it here.
http://www.goldfishutopia.com/product_info.php?cPath=19&products_id=352

If your fish are not eating anymore, then you need Prazipro or Droncit for possible cestodes. Both meds are praziquantel-based and available in online stores and petstores, or veterinary clinics respectively. Droncit is sold as an anthelmintic for cats and dogs.

Nematodes can be destroyed by fenbendazole or hopefully the medicated food I suggested earlier as it has levamisole which does that job.