Carbon

[mbu man]

ive got 2 external filters one is a fluval 304 that has got sponge and the biomass stuff that looks like hula hoops in, the other is a 405 that has got the sponges in the biomass stuff in the bottom trays and has carbon in the top 2 trays. it came free with the filter and my LFS said that it would make my tank lovley and clear.
is it ok to have this in?

 

[AK77]

Yup. Its activated charcoal. It absorbs many impurities in the water. It can leech these impurities back into the water though if not changed at the recommended rate. Its usually a good idea to run rowaphos at the same time, as charcol/carbon can release phosphates into the water.

 

[mbu man]

i see, when i had it in my tropical tank it killed off all my plants quicker!
rowaphos? what is this then? where does that go in my other external filter?

 

[AK77]

Rowaphos is just a brand name for a phosphate absorbing compound that goes in your filtration system somewhere. I have a pouch thats in the sump near the return pump, so it has a good amount of water flowing through it and is reducing the phosphate levels nicely.