petsmart carries prime http://www.petsmart.com/product/inde...ductId=2753920
.. personally i wouldn't use topfin .. i've used it before as it came as a sample when i bought my 29g tank kit .. and it stank up sooo much like rotten eggs (a lot worse then how prime smells) that i was uncomfortable using it as my water conditioner ..
prime is 2 drops per 1 gallon 100mL (3.4oz) bottle cost $5.99 treats 500 gallons
top fin is 1 ml per gallon 4oz. bottle cost $4.29 and only treats 120 gallons
you would be saving yourself a lot more money investing in prime .. even if the 100mL (3.4oz) bottle of prime is more expensive then the 4oz. bottle of top fin
if your looking for a water conditioner that has slime coat enhancers .. API stresscoat is a better investment then topfin