Freshwater Aquarium/Goldfish not acting right
I have a 29 gallon tank with a filter (I think it's called a bio-wheel) and 2 goldfish plus a bristlenose pleco. Also in the tank is a Coliseum with a bubbler, a cave and small Driftwood. Recently I added my pleco and it seems since then my goldfish have been stressed. They lay on the bottom more and the one swims around frantically at times. I do weekly water changes and got my water tested just to make sure it was good. The aquarium store clerk said my water was perfect and suggested some salt. I put the salt in like it says on the box but my fish still have not gotten better a week later. They don't appear injured either and the pleco doesn't seem to bother them when it's out (although I don't know about nighttime). I have on occasion seen the one goldfish poke at the pleco which the pleco responds by a wiggle. Do you have any suggestions on how to help my fish? Thanks!
Most scaleless fish don't do well with aquarium salt so it should only be used for medicinal purposes. Long term use of salt in freshwater tanks has been shown to cause kidney failure in fish. I don't recommend it if the fish are healthy.
As for the goldfish I would recommend you purchasing the API Stress Coat. As the name suggests, it prevents and alleviates stress. In addition to that, it also heals minor wounds and acts as a tap water conditioner.. You can purchase this item at Petsmart for around $6.
Here is a link for your convenience: http://www.petsmart.com/fish/water-conditioners/api-stress-coat-tap-water-aquari
I hope this helps!