Vodka dosing finally kicked in; now what?

[Dan_P]

I think of phytoplankton as photosynthetic (autotrophic) plankton.

Reef tanks don't have diatoms, dinoflagellates, cyanobacteria, etc. floating in the water? To be fair, I should have also asked how many of these things per mL do you think are floating around that you consider not many.

For my fish only system, I count 25-100 dinoflagelates per mL and 25 diatoms per mL. That's just two species, presumably photosynthetic by their color. There are more of the "œother" green and golden brown things. I get the count by centrifuging 500 mL tank water at 4000 rpm for ten minutes and resuspending the pellet in a small known amount of tank water for a count. This could even be an underestimate because of the short centrifuge time. My tank's skimmate contains tens of thousands per mL.

So was your estimate based on gut feel or do you know of someone actually counting the organisms in a reef system?

 

[Dan_P]

My understanding is that cutting off the carbon supply suddenly will kill the bacterial population that has been built up, causing an large drop in oxygen and potentially killing a lot of stuff. Is that not accurate?

Bacteria are not so easily killed for one thing (if it helps, Randy doesn't think so either). For another, they may not die like multicellular organisms, that is drop dead and decompose. For example, they might form spores. In an event they will slow down their metabolism first and continue to maintain their internal machinery as long as possible. In the mean time, predation by protozoa, nematodes, etc. and death by phages would continue as during dosing but now with the effect of a population reduction.

By the way, if you accept that carbon dosing works because of biomass formation and exporting through skimming, there won't be much bacteria sludge or floc around to be effected by a sudden decline in a carbon source. If that's wrong, then there willl be slime, floc or sludge left behind that will be disappointed but probably not drop dead.

A large drop in oxygen occurs from a large amount of metabolic activity, like from carbon dosing or a lot of organic matter decomposing, not from a couple of grams of bacteria suddenly dying (which they probably won't) and being consumed by other bacteria, protozoa and sponges.

I plan on a complete, all at once shut down on dosing when I reach the maximum level in December.

 

[Dan_P]

I think the dose reduction is just the first step in determining how much carbon is need to maintain desired levels. It could be that there would be not impact to just stopping. IMO, more importantly, nothing should ever be done all at once in a reef tank.

I agree John.

 

[bertoni]

Wouldn’t you want to determine if the system is still producing nitrates in excess of the system’s non-fed denitrification capabilities by ending carbon dosing (either stopping or rapidly rampling down) and monitoring nitrates for a few weeks, resuming carbon dosing only if necessary?

Ending carbon dosing immediately might be fine. We don't have useful data on what might happen, though. If you just want to know whether the tank is producing nitrate, then dropping the carbon might tell you that, but various organisms might react badly, at least in theory.

 

[bertoni]

Reef tanks don't have diatoms, dinoflagellates, cyanobacteria, etc. floating in the water? To be fair, I should have also asked how many of these things per mL do you think are floating around that you consider not many.

For my fish only system, I count 25-100 dinoflagelates per mL and 25 diatoms per mL. That's just two species, presumably photosynthetic by their color. There are more of the "œother" green and golden brown things. I get the count by centrifuging 500 mL tank water at 4000 rpm for ten minutes and resuspending the pellet in a small known amount of tank water for a count. This could even be an underestimate because of the short centrifuge time. My tank's skimmate contains tens of thousands per mL.

The topic in question is dissolved nutrient reduction, so I would be more specific by saying I don't believe that phytoplankton does much in the way of filtration. My belief here is based on the lack of any nutrient response to a new UV unit appearing on a system in any case of which I'm aware.

 

[RobZilla04]

Ending carbon dosing immediately might be fine. We don't have useful data on what might happen, though. If you just want to know whether the tank is producing nitrate, then dropping the carbon might tell you that, but various organisms might react badly, at least in theory.

FWIW I immediately stopped dosing carbon (from 25ml daily in a 90g system to 0) at once. No ill effects on any of the inhabitants or coral. Over the course of the following 6-8 weeks nitrates and phosphates began to climb drastically. Nitrates went from 2-5ppm to over 80ppm. Phosphates from .08-.1ppm to .45ppm.

Working on getting back into the reduction through carbon dosing again paired with GFO in a reactor.

Slowly of course.

I believe you are aware of the thread regarding my issues.

 

[Dan_P]

FWIW I immediately stopped dosing carbon (from 25ml daily in a 90g system to 0) at once. No ill effects on any of the inhabitants or coral. Over the course of the following 6-8 weeks nitrates and phosphates began to climb drastically. Nitrates went from 2-5ppm to over 80ppm. Phosphates from .08-.1ppm to .45ppm.

Working on getting back into the reduction through carbon dosing again paired with GFO in a reactor.

Slowly of course.

I believe you are aware of the thread regarding my issues.

Nice demonstration.

How quickly did nitrates increase from 5 to 80 ppm?

 

[Dan_P]

The topic in question is dissolved nutrient reduction, so I would be more specific by saying I don't believe that phytoplankton does much in the way of filtration. My belief here is based on the lack of any nutrient response to a new UV unit appearing on a system in any case of which I'm aware.

I think that I understand. Let me play it back. A new UV did not result in a change in nitrate or phosphate concentration. Assuming a high kill rate, death of all those pelagic organisms with no measurable nutrient level change points to them not playing a major role in nutrient consumption/production.

How's that?

 

[RobZilla04]

Nice demonstration.

How quickly did nitrates increase from 5 to 80 ppm?

6ish weeks. Partly I blame my heavy feeding but nonetheless they would've continued to climb either way.

 

[Dan_P]

6ish weeks. Partly I blame my heavy feeding but nonetheless they would've continued to climb either way.

Did you consider restarting dosing before 80 ppm was reached?

I posted an observation on yoyo nitrates, levels that went up after feeding but came down during next day's photo period (a lot of macro algae) and went to zero when I cut the feeding in half. I measured nitrates every 4-6 hours. Maybe, when nitrates are under control again, you might be able to perform a similar study to determine how much nitrate your system can handle before it starts to climb.

 

[RobZilla04]

Did you consider restarting dosing before 80 ppm was reached?

I posted an observation on yoyo nitrates, levels that went up after feeding but came down during next day’s photo period (a lot of macro algae) and went to zero when I cut the feeding in half. I measured nitrates every 4-6 hours. Maybe, when nitrates are under control again, you might be able to perform a similar study to determine how much nitrate your system can handle before it starts to climb.

The last time I tested Nitrate levels they were between the colors (80-160ppm)on the API card. Totally not the best test kit, I know. The point is they were continuing to rise.

I was seeing LPS trumpet coral dwindle along with no growth. Two to four days after water changes (15% or so) everything would perk up, but then fade and look limp. Nothing has been growing this year other than a species of birdsnest and a couple torch/hammers.

With 80+ Nitrates, .457 Phos, and the mentioned visual observations I decided to get back into Carbon dosing and GFO. Also going to do weekly water changes for a bit to see if I can correct whatever is going on with some solid "acceptable range" numbers. I just wanna get back to a stable thriving system, so studies aren't my thing.

In an attempt to not stray from the topic at hand, simply cutting carbon all together didn't create a problem for me. Perhaps I did the opposite earlier this year and ramped up the dosing amount too quickly and/or too high.

 

[bertoni]

I think that I understand. Let me play it back. A new UV did not result in a change in nitrate or phosphate concentration. Assuming a high kill rate, death of all those pelagic organisms with no measurable nutrient level change points to them not playing a major role in nutrient consumption/production.

How's that?

Yes, that'd be my current guess. I emphasize "guess" because it's hard to be sure. I'm not sure that I'd say I'm convinced, though. Another possibility is that other organisms can being to take up the slack.

 

[bertoni]

FWIW I immediately stopped dosing carbon (from 25ml daily in a 90g system to 0) at once. No ill effects on any of the inhabitants or coral. Over the course of the following 6-8 weeks nitrates and phosphates began to climb drastically. Nitrates went from 2-5ppm to over 80ppm. Phosphates from .08-.1ppm to .45ppm.

Thank you for the data point. If we get enough more people with experience like this, I won't be quite so conservative on the topic of stopping carbon. The carbon seems to have been helping with the dissolved nutrients, though. That's interesting, too.

 

[reefgeezer]

FWIW I immediately stopped dosing carbon (from 25ml daily in a 90g system to 0) at once. No ill effects on any of the inhabitants or coral...

Man, I'm doing something wrong. I just look at some of my corals the wrong way and it seems like there are ill effects! I had a small SPS colony RTN just because I talked bad about it. :lol2:

 

[Dan_P]

The last time I tested Nitrate levels they were between the colors (80-160ppm)on the API card. Totally not the best test kit, I know. The point is they were continuing to rise.

I was seeing LPS trumpet coral dwindle along with no growth. Two to four days after water changes (15% or so) everything would perk up, but then fade and look limp. Nothing has been growing this year other than a species of birdsnest and a couple torch/hammers.

With 80+ Nitrates, .457 Phos, and the mentioned visual observations I decided to get back into Carbon dosing and GFO. Also going to do weekly water changes for a bit to see if I can correct whatever is going on with some solid "acceptable range" numbers. I just wanna get back to a stable thriving system, so studies aren't my thing.

In an attempt to not stray from the topic at hand, simply cutting carbon all together didn't create a problem for me. Perhaps I did the opposite earlier this year and ramped up the dosing amount too quickly and/or too high.

OK thanks. That's a great clarification.

 

[Dan_P]

Yes, that'd be my current guess. I emphasize "guess" because it's hard to be sure. I'm not sure that I'd say I'm convinced, though. Another possibility is that other organisms can being to take up the slack.

Thanks. Yeah, tough to be certain without a $1,000,000 research grant.

 

[bertoni]

Hmm, $1,000,000 might go a ways.