I usually never do this with brands... but we ABSOLUTELY HATE the IM Hydro Fill top offs. In my opinion one of the worst ones on the market. We pulled every one we had out on the field after many issues with them.
We stick to... Smart ATO Micros, Tunze, or JBJ. With out current favorite by far being the Smart ATO Micros. We use them on everything from Small Biocubes to 200 gallon reef systems.