Convinced of a link between GFO and Cyano (and not the good kind)

[asylumdown]

Originally Posted by Myka

What you're describing is common phenomena. The cyano bloom happens in our tanks from GFO for the same reasons it happens with biopellets - quick, significant lowering of phosphate. In other words, too much GFO (or too aggressive with biopellets). It can happen with Lanthanum chloride (FozDown) too for the same reason. It doesn't happen in every tank though under what appears to us to be similar circumstances which is obviously frustrating. Just as frustrating as high nutrient SPS tanks that get no waterchanges or dosing and grow SPS like weeds for years and years (lol). Anyway, the reason the cyano appears is because the water column is suddenly barren of phosphate yet the substrate and rock is still loaded. As the phosphate leeches out of the substrate and rock the cyano jumps in to feed off it as it leeches. Cyanobacteria are extremely efficient at processing phosphate.

The fix: Pull the GFO. Keep using carbon. Add a filter sock, then use a piece of rigid airline tubing with flexible airline tubing attached to make a mini siphon hose and suck the cyano out of the tank at the peak growth of the day (usually at peak lighting). Do this daily or every second day. After you suck out as much as possible use a turkey baster to blast every nook and cranny in the rock. Then use a feeding stick or the baster to stir up the top 1/2" of sand. Wait an hour and remove/change out the filter sock. It takes elbow grease, but it's very effective.

Next time, don't use so much GFO. 1 tbsp per 30 gallons changed out every 2-3 weeks is much "safer" than adding a whack and changing it out every 6-8 weeks.

Added note... in my experience, mature tanks shouldn't need GFO, and usually do better without it.

This is the common wisdom I'm suspicious of. There's never been any evidence or experimentation to show that this is true, it's just what people have surmised because they couldn't explain what they were seeing. But when you start to dissect it from a biological perspective, the notion that suddenly lowering phosphate levels would cause cyano bacteria doesn't make much sense.

1. If cyano is so good at taking up phosphate, it should do as fine a job pulling it out of the water column as it would out of the rocks. It wouldn't not grow when there was plenty available for cheap and easy in the water, then suddenly start growing when the easier to get at stuff disappeared. Chemicals diffuse along gradients, so cyano taking phosphate out solution directly above the rock it sits on top of will create micro gradients that phosphate can move across, regardless of the concentration in the water column. Further, there's good evidence to suggest cyano biofilms have multiple mechanisms that would allow them to actively harvest phosphate in the rocks they sit on top of (micro pH gradients, oxygen gradients, CO2 gradients, direct microbial weathering, etc), which is probably why it seems to favor recently exposed coral skeleton, as that stuff is loaded with phosphate. I can't think of a reason why reducing phosphate levels in the water column would enhance that activity that holds up to close scrutiny.

2. We like to think gfo reduces phosphate levels to "zero", but the truth is that even the most heavily gfo filtered tank water still has as much or more (usually MUCH more) dissolved phosphate in it as most wild reefs. On average it keeps it low, but phosphate levels moment to moment fluctuate in a tank (ie, right after feeding), even if the long term average is "low" due to gfo. If corals and coralline are growing, and you have to wipe your glass down ever, there's enough phosphate to support cyano, regardless of what your test kit tells you. I can also go on and give you reasons why hobby grade (and even some lab grade) phosphate test kits are pretty much never accurate within the range relevant to reef life, but that's another rant.

3. Cyano bacterial biofilms, which can achieve staggering amounts of surface area where 100% of the tanks volume flows over them every few minutes in the immediate vicinity of where phosphate (aka food) is added and broken down will almost certainly be better competitors for nutrients than a teeny tiny reactor in the sump, fed by a teeny tiny pump with flow throttled so the media barely bounces. Over time it brings down the phosphate level for sure and maintains it there on average, slowing the growth of algae, but that doesn't mean lots of other organisms don't have a chance to get some of it first.

Basically I'm saying I think that explanation has a lot of holes in it, and it's never been based on any evidence, or even a biologically reasonable theory. When you add a substance to an ecological system, and suddenly massive growth of a previously absent or minor organism occurs, the simplest (and therefore usually true) explanation is that that substance was a previously limiting nutrient for that organism.

We twist ourselves in knots trying to explain things we see in aquariums by invoking complicated "balance of the system" explanations that survive because they fit well within the narrative we tell ourselves about our tanks, and are virtually untestable.

The more simple answer is that even in a bio pellet or gfo treated tank, there was and always will be enough major nutrients like N and P for certain problem organisms like cyano grow, but that cyano can directly use the organic carbon or rust particles (or both) sloughed off in to the water column as food or an otherwise limiting nutrient.

In the case of gfo, there's plenty of scientific evidence to support the link between iron feeding cyano, but virtually no evidence to support the line of reasoning most aquarists have used to explain this sort of thing.

[Myka]

Iron certainly does feed cyanobacteria (and pretty much any algae too), that's not a big discovery.

What I don't agree with is the iron being the trigger for the cyanobacteria. My opinion, based on my own experiences as well as hearing/reading talks by leading aquarists/biologists is that it is the imbalance of phosphate between the water column and the substrate that is the trigger. It's nearly impossible to keep cyanobacteria out of a reef tank, so it's the trigger for the explosion that you want to avoid. I've seen cyanobacteria in new tanks where old rock was used, and new saltwater was used. Also causing this imbalance. No GFO.

Cyanobacteria is certainly in the water column when it is on the substrate/rock. Think of the cyanobacteria clinging to the rocks like the fish swarming for the food. Most tanks have enough water movement so the cyano can't form clumps in the water column, but it certainly will if the water is not moving enough. In cases where there is a lot of cyano, I've often seen it floating in clumps in areas of low flow.

Keep in mind there are thousands of species of cyanobacteria.

[asylumdown]

Originally Posted by MitchM

I have a CPR 4 inch sock holder mounted inside the sump with a maxijet 600 pumping sump water into it.

The dosing tube drips into the filter sock.

This is a great idea. I can run something similar off the manifold on my return line, and switch my gfo reactor to a carbon reactor.

[MitchM]

Originally Posted by asylumdown

This is a great idea. I can run something similar off the manifold on my return line, and switch my gfo reactor to a carbon reactor.

Thanks. The sump water is also filtered first through a 200 micron sock from the display tank.

[asylumdown]

Originally Posted by Myka

Iron certainly does feed cyanobacteria (and pretty much any algae too), that's not a big discovery.

What I don't agree with is the iron being the trigger for the cyanobacteria. My opinion, based on my own experiences as well as hearing/reading talks by leading aquarists/biologists is that it is the imbalance of phosphate between the water column and the substrate that is the trigger. It's nearly impossible to keep cyanobacteria out of a reef tank, so it's the trigger for the explosion that you want to avoid.

I'm not saying you can keep cyano out of a reef tank. But I am saying that the idea of an 'imbalance' as we tend to apply it to aquariums is a biologically meaningless term, and there's never been (that I've ever been able to find at least) any research in any kind of an analogous natural system that would support that idea. If it's an "imbalance", what would constitute a "balanced" state? There's always going to be phosphate in the system somewhere. In older tanks, there's going to be a great deal of it in the rocks from a few different sources. Cyanobacteria doesn't care care whether the phosphate is in the water column or the rocks, if it's there and accessible, and it has everything else it needs, it will grow.

The idea that reducing the total amount of dissolved phosphate in the tank could somehow make phosphate more available to cyanobacteria doesn't make sense. In a tank with no cyano problem, one of three possible states is true:

1. There is no cyano in the tank (virtually impossible if you've ever added a coral, fish, or piece of live rock from another tank or the ocean)
2. There is a cyano predator keeping it in check (if you could identify this predator and breed them, you'd be rich. Or rich-ish)
3. The nutrients needed for cyano to become dominant are not available in sufficient quantity.

Case three is most likely. If you add one chemical intended to lower the level of one nutrient (GFO, biopellets, etc.), and then you see an outbreak of something like cyano, it is far more likely that what's actually happened it that you've not reduced the target nutrient low enough to become limiting to said organism, while adding another nutrient that previously was.

Originally Posted by Myka

I've seen cyanobacteria in new tanks where old rock was used, and new saltwater was used. Also causing this imbalance. No GFO.

I'm not saying you need GFO for cyano bacteria to grow. What you need is all the nutrients it requires to become dominant present in excess to grow. Old rock in new water might be a perfect example of that case. We only do 10-20% water changes at a time, so without intentional addition, over time the iron levels in a tank will fall, especially if you've got algae of any kind growing. 100% new water has whatever background iron levels were present in the salt mix (potentially quite high depending on the source), and nutrient laden rock that, depending on the rock, has the capacity to raise dissolved phosphate levels by 0.5 to 1 ppm in a couple of days.

Originally Posted by Myka

Cyanobacteria is certainly in the water column when it is on the substrate/rock. Think of the cyanobacteria clinging to the rocks like the fish swarming for the food. Most tanks have enough water movement so the cyano can't form clumps in the water column, but it certainly will if the water is not moving enough. In cases where there is a lot of cyano, I've often seen it floating in clumps in areas of low flow.

Keep in mind there are thousands of species of cyanobacteria.

I agree there is cyanobacteria in the water column to some degree, but the kind of cyanobacteria that forms mat-like biofilms that are problematic in reef tanks are most likely not the kind that have much or any of a pelagic phase. The mat forming cyanobacteria that we deal with are probably species from the genus Oscillatoria, which form long, oscillating filaments that form dense mats on top of substrates. They reproduce by fragmentation, and unlike dinoflagellates that can let go of the substrate and move in to the water column and swim around, the only amount of time most Oscillatoria species spend in a pelagic 'phase' is when hormongia (lengths of filamentous segments) break off from a parent colony and get blown to somewhere else that they settle to start a new colony.

Pelagic cyanobacteria are from a different group of genera and are mostly non-colonial forming, single celled organisms that wouldn't last long with a protein skimmer and even the smallest amount of mechanical filtration. The exception are species from the genus Nostoc, which can form massive floating mats (perhaps what you've observed in tanks with poor flow), but under adequate flow and decent filtration they'd likely be quickly destroyed and removed. Basically I'm saying that the kind of slimy, substrate coating, mat forming cyanobacteria that we deal with don't pick between being in the water column or being on the rocks depending on conditions. If you're seeing more cyano on your rocks tomorrow than you saw yesterday, it's because the total mass of it in your tank is increasing, not that it's picking a substrate bound state over a pelagic state (otherwise our tanks would look like a red tide).

[asylumdown]

Originally Posted by MitchM

Thanks. The sump water is also filtered first through a 200 micron sock from the display tank.

I picked up Phozdown tonight, but stupid home depot sent me on a city wide run around looking for the half inch PVC fittings I'll need to modify my manifold, so I won't be able to set it up until the weekend.

I also picked up a 100 micron filter sock, and some 50 micron filter fabric to put in it that will live in the filter second filter sock holder in my sump that I've never used to dose the phozdown in to. I'm a little nervous about calibrating it all properly as I don't really trust most phosphate test kits (thus it's hard to trust the "rate" at which phosphate is added to the tank), but I'll start slow and see how I go.

[MitchM]

I don't know what section of town you're in, but I find that Rona at Crowfoot has the best pvc fitting selection.
I started out dosing 1/2 the recommended daily amount of Foz Down.
For measuring phosphate I use both the readout from my Hanna tester and the appearance of existing macro algae to tell me if things are going in the right direction.

[asylumdown]

Which Rona? When I left the 16th Ave Home Depot I called the Bowness Rona because they're the closest but they said they didn't have anything smaller than 2" fittings. The guy at Home depot said they were the only ones that didn't carry the small fittings though, so I drove all the way to freaking royal oak (after their plumbing department wouldn't answer their phone) and they had the exact same selection as 16th ave. I hadn't eaten dinner yet, so I was hangrily fuming. The next closest Home Depot would have been Country Hills, but that's practically driving to Airdrie and they wouldn't answer their phone either.

Rage.

[asylumdown]

Originally Posted by IanWR

Before you start your LC dosing (which I have not done, so only passing on what I read), I know that Reefsupplycanada used to sell 10 micron socks to use with Fozdown. I would hate to see your tank suffer another mysterious set back that may be ultimately traced to LC flocs that escape your 50 micron net.

That's a good idea. I wanted a smaller micron sock than what I could get at wai's. And as for set backs... If the tank looked the way it did a year ago, I'd be way more cautious about this. But when you've not got much else to lose, it's less scary to experiment.

[asylumdown]

Originally Posted by brotherd

What 1/2 inch fittings are you after?

90 degree elbows. Got to get a pipe from my rerun line back to my filter sock area