Sick Fantail goldfish

Question
I have a sick goldfish.  We recently added a Pecos and ever since our two goldfish seem lethargic and hang out inactive on the bottom of the tank.  Our orange goldfish appears to have blood along his belly and fins.  The ammonia level is 0 PPM, Nitrates and Nitrides are all good.  PH is 7.4.  We are taking the Pecos back to the store.  We may have overfed our fish increasing the daily amount for the additional fish.

Answer
Good morning Bruce, thank you for your question.

Do you mean a Pleco? As in a common plecostomus? I believe that's what you mean. See if he looks like the picture: http://en.wikipedia.org/wiki/Plecostomus

These fish are famous for their ability to keep the aquarium clean, but in my experience, they add an incredible waste load to the tank when they get to be over a couple inches.

If you have your two goldfish in a 20 gallon tank (the mimimum for 2 goldfish) adding a plecostomus would be pushing the limit as far as what it could take for bio-load. Any smaller than this, and you are headed for disaster. These plecos outgrow even 75 gallon tanks! I have seen them grow to 2 feet in the local rivers here, where there is a thriving colony. I believe you are wise to return the fish.

If, however, you bought a Chinese algae eater:
http://www.aquahobby.com/gallery/e_Gyrinocheilus_aymonieri.php

You should know that these fish will suck the slime coat off of goldfish, which could be the reason for the redness. It doesn't sound like you bought a CAE. Please, don't ever!

I would recommend you do a water change, in case waste buildup is what is bothering your fish. Do a 30% water change, up to 50% if you have time, and add 1 teaspoon of aquarium salt (pre-dissolved in warm water) per 10 gallons. This will help to relieve stress. It might not hurt to add fresh carbon, or change the filter cartridge(s).

As long as you keep the water very clean, your two goldfish should be fine. Do keep in mind that when you test the water, both ammonia -and- nitrites must be 0 ppm. Even though detectable nitrites are not as toxic as ammonia, they are still quite toxic and will cause your fish discomfort. Nitrates no higher than 20 ppm are acceptable.

I hope that helps! If you haven't yet, check out http://www.kokosgoldfish.com and http://www.goldfishparadise.com - both sites are my two most highly recommended goldfish sites.

Take care!
Nicole