Super high nitrates, low (ish?) phosphates, coral frags not so good

[bureau13]

I have a 240 gal tank that's been up and running for at least ten years, but let's just say I had some issues and neglected it for quite a while. I'm back trying to get it going again. It's got sand and live rock and a refugium, all of that has been there since the beginning, there are 6-8 fish (can't find two, so who knows, story for another thread). I jumped the gun a bit with a bunch of small coral frags, and most fo them just kind of faded into nothing. Lots of possible reasons for that of course, so I've decided that was dumb and I need to get my nutrient levels under control.

Since I started measuring (Salifert) I'm getting what looks like 100ppm nitrates and between 0.03 and 0.1 phosphate. You know the color matching stuff, it's hard to be precise, but this is pretty consistent. In that time, I've done multiple water changes of ~100 gallons using NSW, I'm dosing 30 ml per day of "DIY NOPOx" (50% vinegar, 38% vodka, rest RODI) and running a small Seachem DeNitrate reactor just for fun. I have a small ball of chaeto in the fuge lit by a Kessil H80. The chaeto may have grown a bit but not very much. I did have a pretty heathy growth of hair algae on the back wall until I put bristletooth tang in there and it's pretty much completely eradicated.

The nitrates are driving me crazy. How are they still so high? I have been doing the carbon dosing for maybe 3 weeks? But previously I was trying straight vodka and it got very cloudy. Still didn't take the nitrates down though.

I guess the elephant in the room is the NSW, I should test that. But even so, I would have though the carbon dosing would have had more of an effect even if I'm starting out high in the source water.

Thoughts?

PS: I'm running the overflow into filter socks which get changed out as soon as they start running over, usually about 3 days, and I'm running an EV-240 skimmer from AquaC, which is producing at least some skimmate.

 

[blaxsun]

The SeaChem reactor probably isn't doing much. Unfortunately I don't have any explanation for the high nitrates; there has to be some other factor that I'm drawing a blank with.

 

[bureau13]

The SeaChem reactor probably isn't doing much. Unfortunately I don't have any explanation for the high nitrates; there has to be some other factor that I'm drawing a blank with.

Yeah, you're probably right. I was thinking maybe that would be a good place for the bacteria to hang out, rather than clouding up my tank, if that should happen again, although it hasn't since I started using the vinegar/vodka mix. I'm also possibly a bit low on the dose there. I'm using the Red Sea (I think?) dosing regimen but in calculating the amount I was probably a bit conservative.

 

[blaxsun]

Yeah, you're probably right. I was thinking maybe that would be a good place for the bacteria to hang out, rather than clouding up my tank, if that should happen again, although it hasn't since I started using the vinegar/vodka mix. I'm also possibly a bit low on the dose there. I'm using the Red Sea (I think?) dosing regimen but in calculating the amount I was probably a bit conservative.

One would've though the refugium would be having a greater impact, but maybe it's already made a huge dent (your nitrates may have been a lot higher). It's hard to tell how much over 100ppm your nitrates were - since most test kits are going to max out at 50-100ppm.

 

[C_AWOL]

It will usually take a while for carbon dosing to catch up to the nitrates created via food input. You'll know it's doing its job based on your skimmer creating a lot more skimmate than usual.

Have you tried doing something along the lines of a rip clean with the sandbed? My friends tank that had high nitrate issues basically went through the same thing as you did (including carbon dosing being ineffective despite plenty of no3 and po4 being present) and after i helped him remove and clean the sandbed entirely, his nitrates finally started dwindling (because many large frequent water changes alone were simply not working)

 

[bureau13]

It will usually take a while for carbon dosing to catch up to the nitrates created via food input. You'll know it's doing its job based on your skimmer creating a lot more skimmate than usual.

Have you tried doing something along the lines of a rip clean with the sandbed? My friends tank that had high nitrate issues basically went through the same thing as you did (including carbon dosing being ineffective despite plenty of no3 and po4 being present) and after i helped him remove and clean the sandbed entirely, his nitrates finally started dwindling (because many large frequent water changes alone were simply not working)

That sounds terrifying, lol. My sand bed has been there for a long time, and is pretty deep in places. I do have some Nassarius snails doing their thing in there, but I always thought that stirring that up would be bad...

 

[C_AWOL]

That sounds terrifying, lol. My sand bed has been there for a long time, and is pretty deep in places. I do have some Nassarius snails doing their thing in there, but I always thought that stirring that up would be bad...

It's definitely not for the faint of heart thats for sure! It was essentially a last resort since he was getting tired of doing so many water changes but after doing that his nitrate hasn't gone past ~20-30 ppm via hanna checker

 

[jda]

The chaeto will grow faster when the nitrates get lower, or at least it does for me. The chaeto also needs iron to grow well, so if you have not been changing water then iron could be depleted.

You do not want to rip clean your sandbed. If the sand has been in place for a long while, then vacuum about 20-25% of it and replace with freshly mixed salt. Do another 20-25% in 3-4 months until you are done. Deeper sand beds are EXCELLENT are removing nitrate, but they can get gummed up with inert materials from fish waste and basically gum up the works. By doing sections at a time, you can let the microfauna repopulate the freshly vacuumed areas before you move on to the next. This doubles as water changes which is the ultimate reset button. The sand might also re-establish the anaerobic zones and start to chew through no3 again.

Carbon dosing can work to reduce nitrate. The bacteria that you are growing will need trace elements in addition to nitrogen and phosphorous. The best way to replace these in the right proportions is to change water, which will also get rid of some nitrates. You need to have a very good skimmer for carbon dosing to work.

You might see some folks suggest that you get an ICP test. This might be fun for you, but spending that money on salt might be better spent until you get things under control. If you do ICP, you will get a sheet of paper, more questions and likely no answers.