Please help me overcome NO3

[tassod]

First some history with my tank and i apologize if this post is too long. Started a tank upgrade from a 125g to a 240g back in January this year. Never had NO3 issues with my 125g which was setup for 1 year.

My 240g has a sump with the following dimensions: 64L X 24W X 20T and I use 3 7" filter socks with it. Have a Trigger Systems Titan Cone skimmer and also running a refugium which basically has mostly live rock in it and some live sand and just recently added some chaeto and mangroves in it.

In the first month and a half of setting up and transferring all my livestock to the tank, my NO3 was nearly undetectable and PO4 was also very close to 0 but i was noticing some of my corals where losing color and somewhat bleaching and I originally thought this could be to low nutrients but later came to realize it was my lights and how they were mounted. Needles to say before i realized this, started over feeding to get those levels up a bit. Well now, not only are they up a bit but my NO3 is 50ppm! I fixed my lights issue, corals look happy now except for some SPS pieces that i have lost for the most part. Getting lots of algae though now, briopsis and Cyano are the 2 big problems.

I also have a DSB which probably is not helping, i went this route because i have several carpet anemones which are my passion and they need at least a 4"-6" sandbed to be happy. I have to add that before my NO3 spike I also tried using some zeovit products (amino acids, potassium, coral snow and zeobak) to see if my corals would color up again and also to try and fight off a very early cyano outbreak. Well that i believe did not go to well as I am certain it caused my sandbed to turn into concrete. Top 1" or so layer turned hard as a rock and also got brown sludge which also hardened.

I don't have too much coral but i do have a very large S.Gigantea and 3 haddoni carpet anemones. As for fish..its a sad story...I had 16 fish..now i have only 9 and they are all in a QT being treated for velvet. So the main DT as it stands right now is fallow and will be this way until December.

I have to admit, I don't do many water changes and when i do, it is only about 20-25g at a time as I don't have large enough containers to hold more for mixing. I added a GEO sulfur denitrator (418 series) about 3.5 weeks ago but it has not even put a dent in my NO3 problem as the effluent output of that reactor is only able to keep the NO3 at zero at a rate of about 15-20ml/minute.

In doing some research, lots of people report that even after doing several large water changes to their systems, the nitrates just come right back up and this is holding me back at even trying to attempt to go that route but if i have to I will. Should i start carbon dosing? Where would i begin with that? Can I do that along with the sulfur denitrator? My PO4 level BTW is 0.08 checked with Hannah. I do run carbon and GFO. I just want to get my NO3 back down to <5ppm...please help! Again sorry for this long post.

[tassod]

So nobody has any input?

[Dario666]

Sorry to say but big wc would be the best and faster way to bring them down as far as the denitrator it takes time carbon dosing works as well but again takes time both your looking at at least 6 to 8 weeks so again big wc would be the fastest way to bring them down and then letting the denitrator to do its thing once you have everything under control small weekly wc at 10% to 15% would be best to keep things healthy noting can replace good husbandry

[bertoni]

Hmm, I thought I had responded. Sorry!

If your substrate is coarse enough to trap a lot of debris, it might be part of the problem. Otherwise, I suspect the nitrate the result of a feeding rate that is adding fixed nitrogen at a faster rate than the filtration can remove it. There are lots of approaches to handling this sort of problem.

Carbon dosing is a reasonable approach to try, in my opinion. You could check the feeding levels, as well, and better skimming can do a lot.

[tassod]

How much of a drop should i expect in NO3 if I were to do a couple of 100g water changes in a week? I am thinking of getting a 100g rubbermaid container and basically drain my sump completely and clean it out and fill it up with the new 100g of water and then repeat this a couple of days later.

[tassod]

Hmm, I thought I had responded. Sorry!

If your substrate is coarse enough to trap a lot of debris, it might be part of the problem. Otherwise, I suspect the nitrate the result of a feeding rate that is adding fixed nitrogen at a faster rate than the filtration can remove it. There are lots of approaches to handling this sort of problem.

Carbon dosing is a reasonable approach to try, in my opinion. You could check the feeding levels, as well, and better skimming can do a lot.

I'm using Caribsea special grade as my substrate. Is it ok to carbon dose and use a sulfur denitrator at the same time? How do i get better skimming? No feeding going on right now as my tank is fallow.

[overskim]

One thing I have noticed is carbon dosing can fuel cyano in general. That route may be dicey for now, but it may be the best option. Might want to try lights out for a few days.

Chaeto is kind of tricky to get it to start exporting nutrients. Once you get the cells to start dividing it grows like a weed. Dosing iron is also essential to get the process started in a reasonable amount of time. If you want a really hungry algae you may want to try caulerpa. It has some drawbacks though, primarily relocation.

I wouldn't waste that much money on water changes for nitrate, just my opinion.

[bertoni]

The Special Reef Grade is fairly coarse. It might have accumulated enough debris to be a problem. I would replace it, but I prefer finer-grained sand beds. If there's no food going into the system (I think that's what you mean), that makes me much more suspicious of the sandbed. Also, if there's no feeding, the skimmer size is less likely to be an issue. Improving skimmer generally requires cleaning and tuning a skimmer, if useful, or getting another unit.

Using carbon dosing and a denitrator at the same time can work. I'd just watch carefully for signs of problems with any corals in the system, whichever approach you take. I agree that carbon dosing sometimes will fuel cyanobacteria.

As far as water changes, if the total water volume in the system is around 200g (hard to measure that), then a 100g water change should drop the nitrate level by half. I agree that the level will bounce back up rapidly if there's an underlying problem.

[tassod]

Replacing 400lbs of sand might be an issue so I'm not even going to go there. I think my problem was the feeding i was doing. I was feeding 3-4 times a day and those feedings were not small, I used large chunks of frozen food almost daily. I did remove a bunch of sand that was hardened and had changed to a black color on the surface for whatever reason. The tank also had 15 fish in it so the bioload was large. I believe my total water volume is around 280 -300gals with about 80 gals of that being in my sump. I'm gonna do the water changes and see what happens to the NO3 levels and go from there. Hopefully, they get reduced to a workable level for my denitrator to take over and keep them low.