I don't need 50 of them, just 3. One in the system, one being cleaned and one drying = $60. But I believe you can take out too much out of the water. There are organisms that eat those small particles in the water column so why take them out. 200 micron is as small as I would want in a filter.So $20.00 x 50=1000.00 holy smoke batfish, i think the joker got you!