What do you do when carbon dosing doesn't work and you can't grow bacteria in your tank? Start over?

[2Wheelsonly]

I wish I knew the magic ingredient in my tank that's preventing any form of nutrient control.

I simply cannot lower my nitrates, I can't do it. People say "if the corals look great who cares" and my worry is that my nitrates are going up with no end in sight and I simply have no way to get rid of them. I have a 300G tank (350 volume) and decided these past few weeks to buy some 150G rubbermaid tanks. I filled 4 150G tanks with fresh mixed saltwater and test each batch (extremely slight pink almost clear which is expected with regular IO). I have a 6 stage RODI 150gpd unit with newer filters/membranes.

I just changed what I believe to be 600G of water over 7 days. My nitrates are the exact same and during that time my feeding has been so light that I feel guilty for my fish. I am giving my one anthia just enough frozen per day to survive and feeding the tank as a whole 1 time every other day and very small amounts. Nitrates are still dark pink on my test kits (nitrites are 0). Phosphates are sitting at 0.02.

I have tried carbon doing for the past year (as high as 220ml per day of vinegar) and I have 0.0 effect other than the most annoying problem of the foam blowing the lid off my skimmer and not going in the cup. The foam is so thick it blows the lid off the skimmer and if I tape the lid down it shoots air/water so violently through the hole in the lid it makes a mess. Literally 1 year of carbon doing and no effect.

I placed 4 no3 export bio bricks in my sump for surface area and nothing. I also have a sulfur denitrator (aquamaxx TS-2) with over 8 lbs of sulfur in it running for 8 months now and it's not even able to get to 15ml per min before going completely pink (these things are junk anyway so I don't look at this as a real solution, wasted my money on garbage).

My tank was started 5 years ago with live rock, since then added lots of dead rock to craft scapes but for the first 4 years I was always extremely low nutrient. I can only guess my tangs have grown in size over this time and my bio filter can't keep up but it feels no matter what I do I can't tackle this nitrate problem. I refuse to believe it's just in the water, SOMETHING is leeching nitrates, it has to. There is no other explanation.

I am debating tearing it all down and restarting with all new everything. I don't want to spend any $$ on livestock if I know the direction is headed right for a crash. My test kits are so pink I would assume I have 200+ no3 at this point as I just don't know.

 

[Thaxxx]

What test kit are you using?

 

[2Wheelsonly]

What test kit are you using?

I have 3 salifert nitrate kits (all new)
1 red sea pro
1 nyos
1 api

I was really really really really really really hoping it was just a problem with my test kits but sadly it's not. Also had two different LFS cross check my results.

 

[Thaxxx]

Must be the rocks leeching. What's the biggest water change have you done at one time?
I would say do a 75% water change and test immediately. That's got to move the needle some. If it drops at all right after you've done the water change, then goes back up, the rocks and maybe the sand are leeching. If it still hasn't moved. I'm stumped

 

[TriggerFinger]

Have you ever diluted your water sample to see if you can get a measurable result? Half rodi and half tank water?
Do you have a sand bed?

 

[DanConnor]

You did a 200% water change in a week and it had no effect?
That seems unlikely- maybe you levels were so high that it did come down, but not enough to show up on the test.
Can you keep changing that much water for a few more weeks?

I have an opinion about restarting- never do it! You can fight through anything

 

[Nano sapiens]

IME, water changes in SW only have had a short term effect on nitrate, but within a day or two the levels returned right back to where they were. They are much more effective in FW.

I'm surprised that vinegar carbon dosing didn't have a noticeable effect on the NO3 level (I just completed a successful round with a lot lower vinegar-to-water ratio than you used). Did you notice white bacterial buildup on the glass, rocks or other surfaces?

Have you used any commercial products for cyanobacteria/algae control that might have damaged your microbiome (bacteria/archaea)?

 

[DanConnor]

I could see water change only having a short term effect in a small tank- but this is 300 gallons. What could be polluting it that fast?

 

[2Wheelsonly]

I have a sandbed, it's fairly clean as I have a diamond goby that's been busy for the last 4 years. It's roughly 1.5 inches with some bare spots as my tank flow is 100x. Sand has never been changed out in the 5 year history.

I tried dilution still hard to read but "think" my nitrates are 25-50 but seem to be rising. When I sent my water to be tested it say 40.

I tried vinegar for 1 year straight on a doser. Got it all the way up to 200ml /day. I tried a vinegar/vodka mix, also a straight vokda. I also tried nopox, mb7, and dr tims over this past year. Nothing had an effect, no blooms...nothing. I can tell something happens as my skimmer cup lid does not stay on and skimate doesn't like to go into the cup when I dose. I also see the oily film form in my low flow sump area with slight white on the front glass instead of algae.

 

[2Wheelsonly]

Wel

I could see water change only having a short term effect in a small tank- but this is 300 gallons. What could be polluting it that fast?

And crazy enough the last change was 150G which still should make a dent (50% was performed on a day I skipped feeding). So in 24 hours after change NOTHING was added to the tank and nitrates were through the roof. The smart people say nitrates can't leech and are only in the water...well I think I must have proven that theory wrong! I should reach out to Harvard and see if I can get an honorary PhD for this break through discovery!

 

[Thespammailaccount]

I know that you need phosphates in order to carbon dose to reduce nitrates maybe your phosphate level is too low?

what is your nitrate level coming out of the sulfur denitrator?

 

[Deschutes541]

What mechanical filtration do you have? Filter socks? If so, I would change them daily.

Also, what is your stock list? You may consider selling some of your livestock to lessen the bioload.

 

[Nano sapiens]

I could see water change only having a short term effect in a small tank- but this is 300 gallons. What could be polluting it that fast?

This is one of those really odd things about reef aquaria and is reported quite often. In my case, I changed 50% of my small system's water and noticed the expected 50% drop in NO3, but within 2 days the nitrate level was right back where it started...with very minimal feeding during the time period.

 

[Nano sapiens]

Some good comments on here regarding phosphate and bioload.

 

[2Wheelsonly]

I know that you need phosphates in order to carbon dose to reduce nitrates maybe your phosphate level is too low?

what is your nitrate level coming out of the sulfur denitrator?

25-30 coming out of the denitrator maybe? If I drop the effluent rate to 15ml per min it's almost 0 (under 1) but if I go anything past that it rises and never catches back up. 15 seems to be my limit with 8 lbs of sulfur.

 

[2Wheelsonly]

What mechanical filtration do you have? Filter socks? If so, I would change them daily.

Also, what is your stock list? You may consider selling some of your livestock to lessen the bioload.

3 yellow tang 1 powder blue, 1 blue hippo, 1 sailfin, 1 clown 1 melanaurus 1 anthia 1 coris wrasse 1 diamond goby. I do have a lot of SPS colonies as my space if fairly limited for new frags and i'm not sure what load the corals create when it comes to no3.

Tank is 300G (96x30x24) with a 50g sump and 50g attached frag tank (no fish). My typical feeding is one small cube of reef frenzy per day (just enough where it gets consumed before it hits the sand). Recently I switched that to once every other day but just a small squirt to make sure the remaining anthia eats daily.

Removing them is not possible without a tear down, my rock work is very intricate and there are LOTS of hiding places (never had issues with aggression in my tank). If anything the comments I usually get from people on youtube about my tank are that I don't have enough fish. People say the same when they see it in person...(great tank but hardly any fish).

 

[DanConnor]

Corals remove nitrate. I have a 8 foot frag tray attached to my sump and I have to dose nitrate to get anything to show up on tests at all. I feed about 1/4 cup of frozen food a day

 

[DanConnor]

The sand could be a pretty big nutrient sink if you've never cleaned it. Maybe try a big water change with a sand siphon?

 

[schuby]

After reading several articles on carbon-dosing (linked to by RHF), I've started dosing my tank. I'm no expert, but based on the articles, I think your tank has too low of a phosphate level. Others have been hinting at this but you are not biting. Do you know why your phosphate is so ultra low? Do you run GFO?

 

[Topekoms]

If you have been dosing carbon it's probably because you are phosphate limited. I would raise my phosphate levels. Also what is your carbon source