If you have the 3 large sponge filters in each tank and they are cycled and you keep up with water changes then the water quality (chemically speaking ammonia etc) would be fine, sponge filters are great at biological filtration and I run them on some quite big heavily stocked tanks with no issues. They are not very good at mechanical filtration (poos etc) so you may end up with some extra waste floating around in the tanks, you can add air powered box filters (no good with fry) to pick up this mechanical stuff though.
It is a very common misconception that you need to spend money to have good water quality. It is all pretty basic really, get water flow through any media bacteria builds up converts and ammonia the ammonia to less toxic stuff and people have been keeping fish with basic filters with no issues for years.
Personally if you were wanting to add a filter to each of these tanks I would recommend aqua one CF1200s they are only $132ea at hollywood fishfarms atm and they flow 1200LPH (roughly obviously drops with media). They filter well and last for years I know people have had them running with no issues for 7-8yrs with no issues, and you can buy many for the price of one eheim. They are the toyotas of filters, cheap and basic and just keep on going And if they do happen to crap out parts are cheap and easy to come by..