It all depends on the size of the chips! Most of the crushed corals sizes i have come across is to large to achieve denitrification. Although this is probably not yout intention with your fuge, anything short of denitrification is gonna be nitrification. Which is something you don't want. I assume you are going this route due to buget constraints. If that be the case, rather go the route of live sand in your fuge. (collected offshore) Another reason I would advise against crushed coral is the restricted variety of lifeforms you will be able to support. A larger variety of life is found in finer sediments than in large sediments. Also more organisms are found in finer sediments than in course.
Larger and less organisms take more time to:
cycle nutrients and grow than smaller organisms.
With the longer growth rate of large organisms to reach maturity, spawning (and therefor food supply to tank) will be less efficient.
By you wanting to go 12-15cm deep I assume you want to achieve denitrification. Else I don't know of any other reason why you would want to go that deep. To answer your question, for denitrification, the clever people say that your substrate should be approx sugar fine. If your cc is that fine then it's fine (no pun).
nice advice guys.was thinking maybe a DSB in my sump.ive got about 30 kg's of crushed coral,im sure you guys are aware its made up of small shells etc... what if i crush it to and extent of making it sugar fine or the size of sand particles,should that work?
mekaeel it would be a mission to crush your substrate to the size grain you need to be effective for a DSB.
lol, I'm having visions of you sitting there with a Chalice and mortar grinding away like a Druid making a potion.
Correct grain size is one of the most critical factors when trying to set up a DSB.
Depending on your budget and how quickly you want the DSB to start functioning, there are various options available from purpose made aragonite substrates to play sand.
Um... I got about 20-25cm with a mixed sub. 25kg's AM Aragonite quite course - bottom layer, then 30kg's coral sand less course, then 19kg's aragamax and 9kg's Aragalive.... I must admit I am a little worried that this was not the best idea but it's in and done so can't change now.... do you forsee any issues with this not working?Sorry if this is off topic