In the past I have used Amquel Plus and Top Fin, which is Petsmart brand, water conditioner and about 4 months ago switched to Prime. Mainly due to cost and amount of water treated per bottle. I have been very pleased with it.
I have been using Prime since I set my tanks up, primarily because the lfs recommended it saying that it is what they use on their display tanks. The only thing about it is that it is a concentrate and can be a tad tricky to measure, depending on your tank size, though it seems to work just fine.