# Marine Aquariums > Marine aquarium Set Up >  living rock rubble

## lost

At the mo i have foam/carbon/bio balls in my fluval and i am going to replace one or two with living rock rubble as i have been told this is a good way to seed my tank.I have not long filled my tank with volcanic rock so i would like to no how many of the canisters of my filter should i use?

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## Timo

Use the carbon at the top (last stage) live rubble underneath, forget the balls and foam IMO.

Make sure this volcanic rock is reef safe, some can release sulphur which is very bad and will kill most marine animals.

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## lost

All the rock either came from a fish shop or were used in a fresh water tank(boiled before being used) so are you saying the last two should have the live rock in? because i found this on the on line manual for the fluval 303
*It cannot be stressed enough that the foam at the top is more than just a good idea ???????????*

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## Timo

> All the rock either came from a fish shop or were used in a fresh water tank(boiled before being used) so are you saying the last two should have the live rock in? because i found this on the on line manual for the fluval 303
> *It cannot be stressed enough that the foam at the top is more than just a good idea ???????????*


Its your pref but i dont use foam or any sponge any more because they can become nitrate factorys. They do help but you need to make sure they are cleaned when needed or they will release.

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## lost

I spoke to the guys at the shop were i get all my stuff from they are very helpfull and they said the same thing so i will dump the foam and just use the two mediums

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## Timo

> I spoke to the guys at the shop were i get all my stuff from they are very helpfull and they said the same thing so i will dump the foam and just use the two mediums


Sounds like a good plan to me  :Big Grin: .

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