Whats better liquid, substrate or solid ball fertilizer

Question

for an aquarium with fish

Answer 1

That depends on the plants you have.  Many of the common species (Java Moss, Java Fern, Water Sprite, Anubias, Hornwort, Anacharis, etc.) draw their nutrients almost entirely from the water column, so a liquid fertilizer would be best.  Others, like Crypts, Swords, lilies, Aponogetons, and such are heavy root feeders, doing best with a fertilized substrate.  Ideally, you'd have a fertilized substrate AND water column, as even the heavy root feeders draw in specific elements through their leaves, rather than roots.