Nitrates and sand depth

[lines_michael]

I have been battling nitrates from the day I moved my already established tank over from my neighbors.

75 Gallon, feed once every other day and have cheato and mangroves in refugium.

Everything else is fine.

My question is, the sand bed is only about 1-1.5 inches deep. Could this be the issue and if so, what is recommended for quality live sand and how much?

Nitrites, Ammonia, pH, Akl, salinity, etc... are all perfect.

 

[bertoni]

A deeper sand bed might help with the nitrate levels. How much Chaetomorpha is being harvested out of the refugium, and how often?

 

[magdelan]

IMHO, more than one inch of LS will release nitrates back into the water colum. Try to keep the sandbed at one inch or less to avoid this.

 

[drummereef]

What kind of skimming are you doing? There is definitely a gray area between a shallow sand bed and as deep sand bed. I'd say stay under the 1" line or go with at least 4-5" to really see significant nitrate reduction in the sandbed. I would find the source of the nutrients and go from there. Are you using any other type of media like filter socks or sponges? Anything that would become a nitrate sink?

 

[lines_michael]

I have a seaclone 100 and a backpak 2 on the back. Both have sponges on the intakes.

A canister filter with a 2" filter in it too.

I am about to switch to a sump instead of the canister, remove the back pak, and put the skimmer below.

I haven't harvested any of the chaeto because I don't know anything about that. What should I be doing?

 

[papagimp]

From what I've read, having less than an inch of sand causes higher nitrates. But just what I've read. I have about 4" of sand in my 55g and no detectable nitrates. What grain size is your sandbed? And it's not crushed coral is it? Larger grain size and shallow sand bed is the perfect combination for a detritus trap. Causes higher levels of nitrates due to the amount of "crap" that gets caught in the sandbed and not in the mechanical filtration system.

You can get more of a DSB effect by using the finer grade sands, which in turns allows for a shallower sandbed. Get sugar fine grade and a 2-3 inch sandbed would probably do the trick. It'll just take some time for it to start effecting the tank. Dont' expect instant results. bacteria needs to colonize the anerobic zones first. Also, adding more live rock may help. You definatly will get some natural nitrate reduction happening deep within live rock where oxygen does not reach.

One last tidbit, I know the tank was already "established" but the move alone could have stirred up enough junk to cause higher nitrate levels, may just take some time to stabalize again.

 

[bertoni]

Lots of tanks have zero nitrate measured with sand levels anywhere from 0 to 7-8". Sandbeds can be a problem if not maintained, though.

Harvesting the macroalga removes the nutrients from the system. Otherwise, the older macroalga chunks get buried, stop growing, and eventually die and decay, releasing nutrients back into the water column. So the refugium needs to be trimmed to export the nutrients and keep the growth rate up.

 

[lines_michael]

How do you decide how much is enough to keep in there and how much is enough to take out?

Leave the amount that allows decent water flow and also gets light?

 

[bertoni]

Yes, having decent water flow, and making sure that all the algal chunks get good light should be fine. In some cases, iron is a useful supplement to add, but that can be left for the future.

 

[papagimp]

Just don't trim too much macro algae out,
Learned that one the hard way, gotta love those cyno attacks!