Phosphate that won't go away

[Clavius]

Sorry to jump into this discussion, even though I'm fairly new to scrubbers.

I do have 7 years of experience with the Zeovit method though. And the theory that P gets stored in the rocks has been an accepted theory in the Zeovit world for many years now. Typically, starting Zeovit in a tank rich in N and P will show the same behaviour. Both N and P go down fast. But P will hit a point in which it "hangs" there for a while because it leaks from the rocks and the sand. It's easy to convince yourself. Just put a little piece of rock from your tank in some rodi water for a week and then measure the P. Often, the solution here is either patience, or dosing CalciumNitrate or PotassiumNitrate to get the balance back. I prefer the first if the balance isn't off by to much.

People are probably going to ask why I'm interested in scrubbing if I'm running Zeovit, so I'll beat them to it: Experimenting. I wanted to see if it will grow algae that outcompete, and get rid of, the brown algae that kept growing on my sandbed.

Only four weeks after installing the little HOG.5, I started seeing all kinds of benefits that I hadn't expected. I started seeing pods again. (They're an endangered species in most zeo-tanks.) I started seeing little swimming and crawling critters that scurry away when I turn on the lights. I've seen a bacteria-bloom for the first time, so my bacterial processes have accelerated. (I had to lower my C dosing (Zeostart) to prevent these blooms.) What I was hoping for: My brown sand has turned white. And the colours of my corals are popping. (Or were those pesky brown algae on my sand also covering my corals?)

So currently my scrubber is making my zeotank work again. I've ordered a second HOG.5, just to see what it does.

[Garf]

Excellent info. So your skimming heavily also ?

If so it fits in nicely with this ;

http://algaescrubber.net/forums/show...ubbers-breathe

Keep us posted of any developments.

[Clavius]

Excellent info. So your skimming heavily also ?

If so it fits in nicely with this ;

http://algaescrubber.net/forums/show...ubbers-breathe

Keep us posted of any developments.

Yes, I'm skimming very wet as advised in the Zeovit method.

[Garf]

I've a feeling that this approach is the missing link in this scrubber imbalance. After all, bacteria and algae compete with each other for both N & P. if we get both to thrive and then remove as much as we can, surely this will ultimately balance the system.
Sounds like carbon dosing alone also suffers the same problems, perhaps both together will do the trick.

Of course there is always a chance that the problem will be amplified. I am hoping that my bubble screen will have some impact on this problem, ie more bubbles using more phos, less bubbles using less phos however even with my optimistic outlook it surely can't be that simple.

[Floyd R Turbo]

Typically, starting Zeovit in a tank rich in N and P will show the same behaviour. Both N and P go down fast. But P will hit a point in which it "hangs" there for a while because it leaks from the rocks and the sand.

None of us are denying that scenario is a reality, what we are trying to point out is that there are several of "us" that cannot attribute our "hanging" Phosphate levels to scenario in the OP, and the OP seems to be directed towards addressing the "nitrate limitation" argument, when it does not - it addresses the rock/sand soaked with Phosphate issue.

So under Zeo tanks, what is the solution to the excess leeching phosphate issue?

[Clavius]

So under Zeo tanks, what is the solution to the excess leeching phosphate issue?

Like I said, either patience and waiting untill the excess phosphates have been processed. Or accelerating the processing of phosphates by adding nitrate. Mostly done by adding PotassiumNitrate, because Zeo tanks tend to be poor in Potassium too.

The Zeo-heads believe that the lockup of phosphates is a result of the use of lime/kalk in the past: http://www.zeovit.com/forums/showthread.php?t=12109
It seems to precipitate the phosphates onto the substrate and rocks where algae can access it directly. I had been using kalkwasser in the past, before switching to ZEO, for a long time, and it explained why there was phosphate buildup in my rocks and substrate.

I never found out exactly how this precipitation process works though.

[Garf]

Sounds like a bit of a red herring to me. Surely if the phosphate is precipitated out into calcium carbonate, then you gotta dissolve the calcium carbonate to bring the phos back out into circulation. You would need to fill a calcium reactor with the stuff wouldn't you ?
i also don't understand the leaching out of the rocks thing. I know phos can bind to organics, but absorbing into rocks ??? If it's just a process of water being trapped in the tiny pores of the rocks then why don't the nitrates also leach out ? If it's due to nitrates being converted to nitrogen leaving the phos behind, then I can't work this out either because the phos should be used by the same bacteria. Any assistance would be good, I don't fancy googling for a day on this, but I will if I have to. This is quite fundamental to understanding problems people are having at the moment. The only possible way I can see for this scenario is if phos is bound to the organics that are on the rock.

[Floyd R Turbo]

I don't fancy googling for a day on this...

Garf, you know this isn't true.

[Garf]

Garf, you know this isn't true.

Damn - you know me too well !! Just trying to see if this leaching effect was a scientific fact, or one of them things that everyone knows because they have been told its true. Just doesn't make much sense to me. If this bonding to the substrate can be released by a gradient, it's not a very strong bond. If its bound to organics which are released through decomposition it makes sense that it's still bonded to a part of the organics but floating around to be sampled and tested. As far as I know, algae cannot utilise bound phosphate ( but will check on this ). This scrubber stuff didn't sound this complicated when I started just 5 months ago.

[SantaMonica]

So we've been giving advice to people on how to size their screen and what to feed based on this and it could have been a fundamentally flawed suggestion.

No, advice was based on watching other peoples' tanks. That's why it takes a while to come up with recommendations.

How did you arrive at the feeding based sizing guideline

Same

can anyone point me to one other person, on any forum, that has posted their phosphate readings from a Hanna meter?

Usually people post how they measure, but not always. A search of the success thread would find it.

You are the one that has to provide the evidence to your claims

No, I don't need to do anything.

Surely if the phosphate is precipitated out into calcium carbonate, then you gotta dissolve the calcium carbonate to bring the phos back out into circulation

No, you just need to reduce P in the water column.

I know phos can bind to organics, but absorbing into rocks ???

It doesn't really bind to organics; it gets "taken up" by (living) organics. Rocks, however, bind phosphate when pH rises, which is caused by phosphate precipitating. When pH falls, the rock and/or calcium phosphate are dissolved back into the water.

If it's just a process of water being trapped in the tiny pores of the rocks then why don't the nitrates also leach out ?

Nitrate does not precipitate out of the water and bind onto rock, thus it cannot go back into the water. Even more, if the holes in the rock are without oxygen, the nitrate will be converted by bacteria into nitrogen gas which will bubble away.

If it's due to nitrates being converted to nitrogen leaving the phos behind, then I can't work this out either because the phos should be used by the same bacteria

No, because those particular bacteria do not need more phosphate.

As far as I know, algae cannot utilise bound phosphate

Correct. Except for dino's, which are mixotrophic.