Kent Phosphate spong will remove phosphate from water.
According to the manufacture it will also remove silicate after phosphate are completely gone.
what is your water source?
if you have tap, consider better source like RO/DI
then you don't have to worry about phosphate etc..
If you can not get a RO/DI unit. You can also look into Walmart, Supermarket etc. They often sell RO water for pretty much aroudn 25-35 cents per gallon.