Battle with slowly increasing NO3 / PO4

heifinator · Mar 31, 2018

Hey all,

I've been having issues with my 93G Cube over the last few months and have exhausted all my local support! Hoping some of the minds on R2R might have some ideas.

This is an SPS dominate system lit with ATI sunpower + nanobox LED arrays (6). Water flow is provided by 2x MP40. Skimmer is a Vertex Omega 180i.

Salinty: 1.025 (Refractometer)
Temp: 77 (Apex)
pH: 7.9 (Apex)
Calcium: 400 (RedSea)
Alk: 7.2 (Hanna)
Mag: 1250 (RedSea)

Nitrate: 40 (API + RedSea)
Phosphate: 0.09 (Hanna ULR)

I have quite a bit of algae, most of it is a pink fuzzy alage and mermaids cup all over all the rock. There is a little bit of GHA but it doesnt take over. Overall the entire tank is covered in a light layer of algae.

What is odd is that after water changes the nitrate continues to slowly creep up. I've knocked it all the way down to ~5 and had it increase back to 40 in a matter of a few days.

For export I run GFO in a reactor, bio-pellets, and do 30% water changes every 2 weeks. I checked the GFO output and it measured at 0.01 so I assume it is not exhausted.

I also dose probidio every 2 weeks for the bio-pellets.

The po4 level seems a little high considering the tank is full of algae and I run so much GFO. Coral health is decent but I am getting some STN on a few acros, overall most of the corals are doing fine. The big issue is the battle with algae.

I have reduced feedings down to ~40 pellets of NLS daily for the 6 small fish in the system.

I am at a loss on this system, I have another system in the same house that is run nearly the same with none of these issues. I feel like the bio load and import are very low so I am surprised to see such high nitrate and po4 levels, especially considering all the algae.

Any help is appreciated!

hijinks7 · Mar 31, 2018

how old is the tank?

heifinator · Mar 31, 2018

Its been running about a year now. Started having a problem about 6 months in. Made various changes to habits / systems over the last 6 months with no noticeable improvements.

I should note that all the rock (pukani) was acid soaked and then cured till no po4 leached, took about 3 months.

djbetterly · Mar 31, 2018

I had a similar issue...tried a lot of different things, in the end carbon dosing in combination with my refugium was the key for me.

jda · Mar 31, 2018

Phosphate is fine. ...nitrate is a little high.

Did you start the tank with dry rock? Do you have sand? if so, then how deep in inches? Depending on the answers to these, I will have some suggestions.

FWIW - You should change the GFO when you change water. It will absorb to an equilibrium with the tank... more P and the GFO absrobs more... less P and it releases some. If you change 30% of the water and the water level P goes down, then the GFO will release some back into the tank. Use less and change it more often.

heifinator · Mar 31, 2018

djbetterly said:
I had a similar issue...tried a lot of different things, in the end carbon dosing in combination with my refugium was the key for me.

I tried carbon dosing before I did bio-pellets. 3 months of NO3-PO4-X. After 2 months I saw no decrease in nitrates or PO4 even following the dosing instructions. All I got was massive cyano outbreaks. Also ran two large cheato reactors, the cheato died. Moved the reactors to my other system and the cheato is doing great.

jda said:
Phosphate is fine. ...nitrate is a little high.

Did you start the tank with dry rock? Do you have sand? if so, then how deep in inches? Depending on the answers to these, I will have some suggestions.

FWIW - You should change the GFO when you change water. It will absorb to an equilibrium with the tank... more P and the GFO absrobs more... less P and it releases some. If you change 30% of the water and the water level P goes down, then the GFO will release some back into the tank. Use less and change it more often.

Dry pukani rock, cured till no PO4 leaching. Seeded with 10lbs cured live rock from LFS. I have 3 inches of sand. I change the GFO with each water change. Every 2 weeks.

jda · Mar 31, 2018

My guess is that you are starving the bacteria that would grow in the sand by promoting growth in the water column with the organic carbon... the anoxic bacteria. Stop carbon dosing (bio-pellets are carbon dosing) and let the tank figure this out naturally.

Your rock is still releasing PO4... or you would not need the GFO. Rock and sand from the ocean can conceal/cover years of high phosphates by binding a lot of it.

I would slowly stop the bio-pellets and remove the P04. Do this over a month. Then, in another month, see where stuff settles out. My guess is that the P will continue to rise, but the N will go down as the anoxic parts of the bacteria start to grow in the sand. Once you see this, then you will need to use some GFO again... but slowly to bring the P down to under .1.

Reefing Madness · Mar 31, 2018

http://www.melevsreef.com/articles/dosing-vodka-why
http://reefkeeping.com/joomla/index...ar-dosing-methodology-for-the-marine-aquarium

http://www.reefedition.com/phosphate-in-the-reef-aquarium-by-randy-holmes-farley/

heifinator · Mar 31, 2018

jda said:
My guess is that you are starving the bacteria that would grow in the sand by promoting growth in the water column with the organic carbon... the anoxic bacteria. Stop carbon dosing (bio-pellets are carbon dosing) and let the tank figure this out naturally.

Your rock is still releasing PO4... or you would not need the GFO. Rock and sand from the ocean can conceal/cover years of high phosphates by binding a lot of it.

I would slowly stop the bio-pellets and remove the P04. Do this over a month. Then, in another month, see where stuff settles out. My guess is that the P will continue to rise, but the N will go down as the anoxic parts of the bacteria start to grow in the sand. Once you see this, then you will need to use some GFO again... but slowly to bring the P down to under .1.

I guess my curiosity with the rock releasing po4 is I soaked this rock in saltwater for almost 3 months. Every week changing the water. By the last month the PO4 level was staying at 0.03 or less even with feeding the bacteria.

I get what you are saying but don't biopellets work by having bacteria populations grown on the pellets and as they get knocked off the skimmer picks them up. Would you not expect that any loss in anoxic bacteria in the sand to be regained from the bacteria growth on the pellets?

I am more then happy to back off the export methods but that is where I started this tank. For the first couple months I just accelerated water change schedule and otherwise didn't have any significant export strategy. Still it resulted in NO3 > 50 PO4 has always been reasonably low, but I am having algae issues so it can't be that low?

It seems to me that backing off GFO would just create more of an issue with algae growth since there is plenty of po4 available for bacteria it seems? I dunno. I'll give dropping the pellets a try slowly. Although I guess I am still a little confused as to the logic of why removing biopellets could reduce nitrates?

heifinator · Mar 31, 2018

Reefing Madness said:
http://www.melevsreef.com/articles/dosing-vodka-why
http://reefkeeping.com/joomla/index...ar-dosing-methodology-for-the-marine-aquarium

http://www.reefedition.com/phosphate-in-the-reef-aquarium-by-randy-holmes-farley/

Thanks! I had read the first two but I hand't seen Randy's phospate article. Reading it now.

jda · Mar 31, 2018

This is a big paradigm shift. I get it.

You kinda have to choose between letting the tank be in control, or you.

The dry rock will set you back a bit - even if it is low on phosphates, it is still likely bound with all kinds of gunk and not yet ready to fully contribute as a dentitrifier. As the gunk gets worked out, it creates more anoxic areas, but also release more phosphate from both the gunk decomposing and also exposing more aragonite structure.

Maybe the tank is not old enough. It can take up to a year for the sand to start converting No3 into N gas. If it is less than a year, then maybe just more time is needed.

jda · Mar 31, 2018

I do not use either on a reef, but FWIW I did find sugar more effective than bio-pellets on a FOWLR. I chose sugar because it was cheap and pure, but it does the same thing as vodka or vinegar (the smell of vinegar is a migraine trigger for me even though it is cheap and pure as well). With this tank, I did not care if I interrupted the in-tank equilibrium since there were not corals who cared if the N dropped fast or even got to zero - I will not risk this in a reef. Other will disagree with all of this.

heifinator · Mar 31, 2018

Appreciate the help. The tank is about 14 months old. It ran perfectly for the first ~6-7 months then my nitrates started to climb. I employed bio-pellets to get the nitrates back down to ~40 but they won't stay below that number.

I am kinda at a loss on this one. Light bio load, light feedings, and a very reliably climbing nitrate level. I guess I can ride it out a little longer and see if things settle out.

jda · Mar 31, 2018

Decaying organics in the rock that are probably contributing to the levels of N and P. It takes a while for them to start to break down. If this is it, it will subside one day.

I feed mostly NLS pellets as well... for the same reasons.

Good luck.

heifinator · May 2, 2018

So an update!

After the help here I made the following changes around April 1 and let the system run for the most part

Reduced photo period to 8hrs total including ramp.
Reduced white / red light by 30%.
Continued to run biopellets in conjunction with a cheato reactor.
Did weekly 20g water changes (~20%) with confirmed 0 TDS source water.
Kept feedings to a minimum
Cleaned filter socks every other day

In addition to this I removed 1 piece of rock every 5 days, scrubbed it, put a h202 paste just on the surface of the rock then rinsed with RODI and reintroduced.

Nitrates have dropped and stayed around 5ppm in the last week and PO4 continues to be <0.01 ppm on a hanna ULR checker.

All forms of algae except the mermaids cup is gone. I am pretty sure I will need to tear the tank down to get rid of this stuff. I scrub it from the rock and 2 days later new "stems" are popping out from the rock, almost like it has roots... I took a piece out and for fun put it in total blackout in fresh saltwater for 14 days, mermaids cup was still alive and well.

About 2 weeks ago I added some GFO in hopes of bringing the mermaids cup growth rate down but my SPS began to RTN a bit even with just 20% of the recommended GFO so I assume PO4 is very very low already.

I can't reduce po4 levels anymore without killing my sps and the mermaids cup just spreads absolutely everywhere. Turning to R2R for some ideas as I'm about to break the tank down and use new cured live rock.

jda · May 2, 2018

Is your tank large enough for a rabbitfish? They destroyed the stuff for me a long time ago.

heifinator · May 2, 2018

jda said:
Is your tank large enough for a rabbitfish? They destroyed the stuff for me a long time ago.

It's a 30" cube so it probably could handle one in the short term. There is a kole tang that nips at the stuff all day but doesn't seem to actually get in. It is extremely well attached.

THX1138CY · May 2, 2018

I had to build one of these https://www.reef2reef.com/threads/poor-man-nutrients-control-donovans-nitrate-destroyer.302685/ my nitrates where over 160ppm did water changes to get it down initially, then built a nitrate destroyer, had to seed a second time and carbon dose it until I saw noticeable reduction, now I have to over feed just to keep NO4 near 10ppm.

heifinator · May 2, 2018

My nitrates are under control now, sorry for the confusion, i posted an update post a few hours ago. Im now fighting a ridiculous battle against mermaids cup.