Rowaphos will help, but you need to get to the source of the problem.
In a tank that small, run some 10% weekly waterchanges with RO/DI water.
What are you doing for maintenance/filtration?
skimmer, penguin125 filter, 2 powerheads...I've started with the weekly RO water changes...I did about a 50% water change and that didnt seem to help much. What causes high phosphate?