Unusual carbon dosing issue

[saltyhog]

I started carbon dosing with vinegar about a year ago due to nitrates rising to 20. I had good success in lowering nitrates to 2.5-5 but had lots of problems with bacterial blooms....white stringy stuff on the underside of corals, on the glass and in the sump. The highest dosing rate I got to was 125 cc per day (tank is 155 gallon with a 42x18x16 sump). I cut back all the way to 50 cc per day and was able to keep nitrates at 5 with that dose. I still had some issues with bacterial bloom evident though.

In Jan of this year I decided to do two things. #1 changed to NoPox and #2 added two Marine Pure ceramic blocks (4x8x8) to my sump. My initial dose was 6 cc of NoPox /day in 3 divided doses during highest pH times in the evening. Dose was deliverd by BRS dosing pump in to the section of the sump containing the Marine Pure blocks. Two months ago I increased the dose to 8.5 cc/day due to nitrates still being a little high.

This has resulted in continued visible bacterial bloom and about a month ago a pretty bad cyano outbreak in the sump only. I held the course as nitrates did decrease to 4 (Red Sea). SPS color and growth has never been great since starting carbon dosing but was acceptable as long as I didn't over do the PO4 control. Two weeks ago my favorite acro colony (grown from a 3" frag) started to STN at the base. A pocillipora colony (also grown from a small frag) also started to STN as well. I stopped carbon dosing abruptly 10 days ago and the STN seems to have stopped. Additionally some of my other SPS has had growth spurts never seen before in my tank. One acro has literally grown several 1/4" + branches in 10 days. Color in almost all SPS has improved as well.

My questions: #1 Why the problem with bacterial blooms at such low dose of carbon dosing (50 cc vinegar and later with only 6-8.5 cc of NoPox). #2 What do I do from here? (so far nitrate still holding at 4).

 

[Kungpaoshizi]

Can't comment on the stringy stuff. I've never seen it with nopox, so I imagine perhaps it's something hanging on post-vinegar. Have you tried a once-over with a toothbrush on a few areas?
As to the RTN, they have it in the nopox or reef energy manual. Something like 'necrosis from the base is usually a problem with too few nutrients'.
I've found this to be true as well, so feeding more, more often, everyday, will prevent that. If nitrates are less than 5, I would cut the dose in half to see how things progress. If you hit a hard zero on phosphates, you'll kill stuff too.

Oh, and never stop dosing a carbon source abruptly, gradually reduce the dose over a week or two. The bacteria you've pushed to grow, will have no food and die all at once for the most part.

Also on another note, I do not have a sump or fuge. No other tank or such that's present. So I know excess bacterial growth isn't happening because it would overrun my entire tank. :) (only 2 powerheads and a tunze 9001 skimmer) I assume this is an issue with vinegar as people will tell you to "get the bacteria to grow elsewhere". I think this goes back to what has been found a major difference between vinegar and ethanol vs methanol. Methanol has slower growing biomass. (that would explain a lot)

 

[Randy Holmes-Farley]

Organic carbon dosing drives bacterial growth, and the bacteria have to grow somewhere. Unfortunately, some people get the bacteria growing in unsightly places, perhaps because of the species being grown, or the relative desirability of other places to grow in your tank.

FWIW, I dosed just upstream of a large rock filled refugium, and I never saw any bacteria, presumably because it was growing down in the rocks. Perhaps there is a better way for you to dose to induce them to grow elsewhere?

My suggestions include dosing some other types of bacteria, say, MB7, and how those grow in a less obnoxious way.

However, there may be so many of the existing species that it may be hard to overcome them, and stopping for a while may be needed.

 

[saltyhog]

Thanks guys!

My hope is that the added "anoxic areas" in the Marine Pure blocks will eliminate the need for carbon dosing. I'm going to refrain from dosing for a while since the tank looks better than it has in some time. I'll follow your advice Randy and dose MB7 and restart NoPox if nitrate starts to climb. It's just weird to get the over growth at what appears to me to be a homeopathic dose of carbon. 50 cc of vinegar or 8 cc of NoPox doesn't seem excessive does it?

Not sure what else I can do as far as changing the dosing site. I'm curently dosing upstream from the ceramic blocks which roughly have the surface area of 200lbs of live rock.

At no point did my nitrate get low enough to be a problem (4 was the nadir). My phosphate has been pretty consistent between 0.02 and 0.04.

 

[Kungpaoshizi]

You might do a Triton test after a bit of time too. There's been some concern about the blocks leaching aluminum so that's something to look out for if things start looking kinda 'bleh'.

 

[saltyhog]

You might do a Triton test after a bit of time too. There's been some concern about the blocks leaching aluminum so that's something to look out for if things start looking kinda 'bleh'.

Good idea, I'll do that! They've been in the sump since Jan. I have read that there is no known toxicity from the observed increased aluminum levels. Is that true?

Right now the tank says "I'm happy" and I've learned to listen to that. I'll check a Triton test, continue to monitor my parameters and watch how the corals are reacting.