i think he was talking to you michail cb 125
there are certain ways to set them. media type is one of the biggest things. with the Korallin being a rapid up flow reactor you need coarse media. like 10-15mm, i use A.R.M. coarse media now (its 10-15mm) you need to set this type reactors drip rate to just past dripping so its flowing-the bubble rate stays low though, mine is set to 25 bubbles with the gtt rate on a steady flow and coarse media work great
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deltec not sure but it a fulidized type reactor and uses a different media, i think you have to use theirs and buy it from them. any rate it uses fine meida.
PM is a slow up flow reactor and uses fine-med media.
the life reef is a down-flow reactor and uses med size media.
in a nut shell, the korallin is the lastest and greatest technology wise.
deltec uses a old but ture technology. not the most effecient but still good. PM is out dated and a fair performer. life reef, just dont know, its oldish technology though.