Its about both. When you have artemia nauplii in that kind of density, both they and the seahorses are giving off waste. Any wastes in any seahorse tank becomes a place where pathogenic bacteria can get fueled.Jumping in to say that this is a great recommendation, and definitely something I am about to start doing myself. I have the bug, I want to start up a small seahorse tank real bad. But the work, and issues with vacations have me worried. I'll be starting live cultures soon to test if I feel this is a viable option or not for me.
Now, I understand the need to keep these tanks clean, as to not foul the water with extra bacteria. This one has me a bit stumped though. Is it less about removing food to prevent bacteria growth, and more about removing now nutrient deficient food? Because they are live, so I couldn't see them fouling much, until they die of course. I would imagine them being live and possibly reproducing would just add a bit more food for the dwarfs?
The dwarfs need optimal nutrition if they are going to flourish so you do not want them filling up on food that is the equivalent of bread crumbs.