Perlite grades and filter speed

[Woolsocks]

OK, just because I can't leave anything well enough alone, I've recently switched from 3um (27-m) perlite to 7um (23-s) perlite in my filter. Clarity is similar, but filtration time and peak pressure have gone up dramatically. You'd think using coarser perlite would reduce time and pressure. What am I missing?

[BigWilley]

Possibly you are letting more crap through the coarser cake that is actually clogging your screens. Maybe you should try precoating with the fine stuff and then body-feeding with the coarser stuff. I have had similar results to what you are describing. IMHO too coarse a filtrate will lead to crappy filtration runs. I'm hardly an expert but I have done what you have done with similar results. Just my 2 cents.

[beertje46]

I believe BigWilley is correct. Maybe add some cellulose fiber to your pre-coat diet.