Idea for stopping livebearer fry getting sucked into filter.

Make sure the filter is not too strong,even when the fry cannot go through,if the filter is too strong,it may be held against the filter water intake.
 
Luca, it will just prevent bigger debris from getting into the filter, it's pre-filtering. Your filter media might need less cleaning, but you will just have to ensure the sponge or netting or whatever you have covering the intake gets rinsed out regularly.
 
The sponge works best because instead of just making the holes smaller, it distributes the suction over a big area, making any one spot less... uh... sucky.
 
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