Not a bad price, but you really should check your water parameters. Aside from compatability, established tanks tend to become acidic over long periods of time from biological activity. If you have a decent level of KH in your tap water, it's less of a problem provided you do weekly partial water changes. It's also a good idea to check the nitrate level occaisonally. Although it isn't as deadly as ammonia or nitrite, it can cause problems if it gets too high.
A FW master test kit is cheaper than losing a tankful of stock. You can find a good price online, then either order one or do a price-match deal at Petco. (Or is it Petsmart that does the price-match?)