Please help, Homemade Sump:nitrate factory or reductor? Pics inside.

[sebwin]

Hi,

I'd really appreciate some help.

I made a sump for my tank a while ago, with all the water passing through a filter chamber of pourous ceramic media.

Originally this may have caused high nitrates, but I was wondering now its half a year old, is it likely to (as my lfs owner suggested) "have formed many anaerobic areas, and now actually be reducing my nitrates".

I have a reasonably high nitrate level at the moment, but that could just have easily been due to lasy water changes etc. I'd really value your opinion.

I have written the full details + photos on this page, with the full question on the end, I'd really appreciate it if youd give me your thoughts on whether to remove it or not.


http://www.sebwin.co.uk/sumpprob/sump.htm

I have sufficient live rock to not need it as a pre-nitrate convertor.

Thanks loads for your time.

 

[reverendmaynard]

If I understand the flow through the sump properly, the water is going up from the bottom of the media to the top. Unless you have an extremely low flow rate (less than 50gph or so) you will never acheive any anaerobic areas doing this. To get anaerobic, you need a small amount of water at a very slow rate flowing through a sealed unit for a long time (1x turnover per hour of the container volume, or so), like a denitrator coil, or you need to only pass the water over the top of very deep media, like a dsb.

So, while it may not be trapping much detritus and creating large amounts of extra nitrate, it is still a bio-active filter that stops at nitrification, never doing any de-nitrification.

IMHO, anyway.

 

[sebwin]

Thanks very much for the reply.

Yes, that is how the filter works, I made it purely for amonia etc filtration as at the time I thought that would be really important.

So you reckon the flow is too high to ever make any anaerobic areas? I was thinking the fact that there was so much of it and a lot of it is that bio ceramic stuff, there might be lots of pores etc which would have become anaerobic almost like a deep sand bed?

So you reckon I should remove it too then?

Do you have any suggestions on what should go in it's place if anything?

 

[Agu]

I have a similar setup but instead of ceramic rings mine has live rock rubble in the first chamber.

There's no way to know if it's increasing or reducing nitrates without removing the media and doing before and after tests imo.

The real questiom would be "Has the media become a mechanical Filter?"

As tightly packed as it appears I would guess the answer is yes. However the fast flow is too high for the nitrates to be converted to N and O, therefore the nitrates are being returned to your main tank. The anaerobic areas depend on slow diffusion to work as a nitrate reducer.

What I've done to deal with the possibility of the rubble in my first chamber becoming a mechanical filter is to "flush the chamber" by adding makeup water to that chamber. A sponge filter on the intake of the return pump is used to catch any waste before it's returned to the tank. You can also use a turkey baster to get the detritus out of the ceramic media.

If you do this you'll probably want to run carbon and keep an eye on ammonia levels. If there's a lot of waste trapped there it could mess up water parameters if you disturb it.


jmo,fwiw,

 

[reverendmaynard]

<a href=showthread.php?s=&postid=6686133#post6686133 target=_blank>Originally posted</a> by sebwin

So you reckon the flow is too high to ever make any anaerobic areas? I was thinking the fact that there was so much of it and a lot of it is that bio ceramic stuff, there might be lots of pores etc which would have become anaerobic almost like a deep sand bed?

So you reckon I should remove it too then?

Do you have any suggestions on what should go in it's place if anything?

Yes. In high flow areas, what you need is large pieces of semi-porous material to create anaerobic areas deep inside them. This is the principal of LR and DSBs. The water flowing around it is high in oxygen, but little of that water actually diffuses into the depths of the material. In those very low flow depths is where the de-nitrification occurs. Your ceramic pieces are just too small to get this effect, IMO.

Do you have adequate LR in your display (about 1-2lbs per gallon) and sufficient flow to allow the LR to be your sole nitrifying filter?

If so, and you are concerned about mechanical filtering, you probably want to use filter floss or something that can easily be cleaned/replaced in that area. Easier yet would be a filter sock on the return to prevent the detritus from entering the sump in the first place.

If not, you need to get more LR, or add on a large remote DSB, or something to aid in nitrification, but that will also provide denitrification. In fact, the RDSB is currently all the rage for de-nitrifying, is pretty simple/cheap to make and use, and doesn't have the drawbacks of an in-display dsb. Here's a link.

Either way, remove the ceramic stuff slowly. Maybe a cup per day or something like that. Check ammonia regularly. If you see signs of it, stop removing the ceramics until it goes back to 0. If it doesn't return to 0 within a week or 2, or keeps climbing for several days, that's a clear sign that your remaining biofiltering is inadequate.