Prefilters are in most of my tanks.
Taco said is true fish nibble at them, and snails and shrimp.
It is very easy to have 2 prefilter sponges to exchange, but I like mine also for their BB colony building ablity so often will rinse and squeeze gently on tank water. But eventually they need a good cleaning because of the gunk and starts to limit intake flow.
I would start with the brand name preflter but some people like the cheap after market variety.
The batch I got shared by a friend from ebay buy, was not as good as the Fluval Edge prefilters I have many of on my tanks. There was a thread here of people's opinions and they varied widely.
My experience for the batch I got was they would not hold their shape well and would collapse in towards the sucton of the intake pipe very quickly. Surely it depends on the density of the manufacturers material, and who knows what you will receive, this time or next time.
If you have sand and you play around with moving decor and plants in the tank much, I would say having one is an absolute. Or if you have fish which might have fry or for shrimp/dwarf shrimp. It also is helpful if you have Malaysian Trumpet or other snails which will get into the intake and usually end up in the impeller area or the pump and jam it up. If not immediately, after they grow larger in the impeller space! They like to eat the gunk in the tubes.
A few of my tanks have not had a prefilter, rare. I will take it off after I have moved things around in the tank leave it of for a time, to help suck up debris and then put it back on. Then do the filter clean out.
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