Thaw it out a bit on a napkin before you feed. Though I don't do this, I read that the frozen liquid contains some phosphates and the thawing liquid will be absorbed more into the napkin than directly into your tank.
Also don't overfeed.
What are your nitrate and phosphate levels?
I guess it depends on what kind of fish you have. I feed pellets, flakes, frozen brine, formula 1 frozen cubes, and seaweed/marine algae.