Fish flashing

Question
I have a 20gal freshwater aquarium that was set up 3 years ago. In the aquarium there are 3 lemon tetras and an albino Rabinbow shark. I have had the tetras for 6 months and the shark for the 3 years. It is heavily planted with plastic plants, rocks/caves for hiding for the shark. I recently (two weeks ago) added an albino bristle nose pleco. I do frequent water changes and run a penguin filter with bio-wheel.

Within the past week I have noticed the rainbow shark is flashing up against the gravel and rocks in the tank. I have not seen any indication of external parasites and he otherwise seems healthy.

I am unsure of how to proceed and do not want to treat blindly. Any suggestions for a cause would be appreciated.

Answer
Christine,  Your bristlenose was probably caught wild and introduced parasites. Your shark will show it first because he is scaleless. Your pleco though scaleless is armored and more accustomed to having them. I am going to tell you the most natural way to get rid of them and you do not have to remove your carbon. I swear by this and have used it for years salt, brackish,and freshwater. It is cheap too...lol Go get Coppersafe. When you add this to your tank it is a mineral and will stay in there for 30 days. The whole lifecycle and abit more of your parasite. If you do a water change before thirty days just add abit more to compensate for what you removed. After your thirty days do a 50% water change and you should be fine. Good Luck, Tina