Question
I have an 800 gal pond with a Savio Excellence Pump and biological filter.  One of my 7" comets has a dime sized ulcer.  I bought Fuba Fix but it does not say how often to use it.  After putting it in, I realized it could damage my biological filter. How often should I use the Fuba fix and what do I do about the biological filter?

Answer
Use the recommended amount for an 800 gallon pond.  I don't remember the concentrations of the active ingredients off the top of my head, so I can't help you determine the size of one dose.  I would say to use one dose once every 4 days for 2 weeks (3 doses).  Then perform a 30% water change and dose one more time.  Wait at least two weeks to dose again.

The most important thing is to keep ammonia and other nitrogen based compounds at a minimum.  I can understand, because of this fact, how wary you are of using the product.  It is personally my favorite anti-bacterial for ulcers.  You could even consider using a contact-applied wound sealant if it gets worse.