Join Date: Oct 2010
Location: Victoria, Australia
What you have to understand is that by overstocking your tank, you are more than likely producing more waste and ammonia than your biological filter can process. Goldfish and plecos are some of the biggest waste producing fish in the hobby, and unless you have a fully established filter with plenty of room for media, you are guaranteed to be seeing spikes in ammonia.
Goldfish are capable of living for well over 20 years. They are more of a commitment than even a dog or a cat. To purposefully cause stunting in any animal is inhumane and unnecessarily cruel. Goldfish are incredibly hardy, and it can be years before you see the ill-effects of improper housing and care. If you truly want to be raked over coals, go onto a goldfish forum and see what they have to say.
Please don't disregard what the people say on this forum as fallacy. I can count on one hand the number of fish and pet store employees whose opinion I respect, and I have been to dozens and dozens of stores in the past few years. Any basic internet search will show that your stocking is grossly inappropriate.
So it is probably poor water quality that is causing issues with your pleco, and until you address the core of this issue you are just going to see an exacerbation of these problems.
If you have a liquid test kit for ammonia and nitrite, please use them and post your results here. If not, please at least go out and purchase them. Even if you are not going to take our advice on tank size, at least do not unintentionally poison your fish.