Deep sand bed or nitrate hot bed
- Thread starter scotty333
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I don't know how a sand bed can harbour nitrates. Do you mean make nitrates? Store nitrates? I am confused.
What is the no3 level in the tank?
As for denitrification, this is somewhat of a complex topic. I have found 2 inches of sand can take tank no3 levels down to near zero - not zero, but close. 3 inches works really well. This is not growth limiting to anything in my experience. However, if the sandbed is very old, then it could be full of inert gunk that can keep water from getting to the lower areas and not work as well. This gunk does not release nitrates or phosphates or anything, it is just in the way. Starting on about year 4, I vacuum about 20-25% of my sandbed every 3 months to get that gunk out. The three month spacing allows the oxic and anoxic zones to establish again and for the micro/pico fauna to repopulate the areas.
What is the no3 level in the tank?
As for denitrification, this is somewhat of a complex topic. I have found 2 inches of sand can take tank no3 levels down to near zero - not zero, but close. 3 inches works really well. This is not growth limiting to anything in my experience. However, if the sandbed is very old, then it could be full of inert gunk that can keep water from getting to the lower areas and not work as well. This gunk does not release nitrates or phosphates or anything, it is just in the way. Starting on about year 4, I vacuum about 20-25% of my sandbed every 3 months to get that gunk out. The three month spacing allows the oxic and anoxic zones to establish again and for the micro/pico fauna to repopulate the areas.
Following. We are building a client tank specifically with deep sand bed. 300 gallon. Dual OF’s. No sump. Reverse flow undergravel with dual sicce syncra sdc 9’s. Copepod filtration. Built many like this for FW with great success.
scotty333
Active Member
It’s not been disturbed for 8 years so is the dark brown stuff 1” + down gunk or denitrification bacteria?
I’m doing a 20% water change tomorrow and am considering sucking it all out
No3 75ppm
I’m doing a 20% water change tomorrow and am considering sucking it all out
No3 75ppm
Vacuum the gunk out. Do only about 20-25%. The sand is not releasing any nitrate, but it is not likely doing a job to reduce them either. Sand bed needs some maintenance every half a decade or so. You might even have to add a bit more as it dissolves with the lower pH down deep.
You have to go really slow in a reverse flow DSB to keep the anaerobic zones going. Lasse does this. If you go faster, then you can have a really good aerobic filter.
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