The pellet size matters, avoid getting small particle varieties. The dust and small particles can get into space between scales and cause irritation… if continued, lateral line disease can begin to show in some species of finfish. (P.s) It is also a good idea to very thoroughly rinse your prepared carbon before introducing it to your pets. As rubbing against itself releases particles. Be gentle with it while rinsing.
Carbon isn’t a necessity but can have certain benefits. Decide if carbon is a filter media you need.