Natural phosphate removal?

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How realistic is it to remove phosphate to reasonable levels via natural/biological filtration?
I have always eschewed wherever possible chemical means but do own some Seachem Phosguard and Rowaphos, the former to get rid of silicates, because it was assumed that the "diatom" algae that I first had in the sump was due to silicates, now a couple of weeks down the line I still have the brown dust-type algae in the sump (the DT has had lights off until now, so hasn't suffered).
I don't really want to use chemicals. For one, they need removing when exhausted, and two, it's another pump to run (using a reactor) and the reactor will need cleaning out and Rowaphos replenishing-I'm trying to keep maintenance down.
So what I don't have at the moment but waiting to go in is a skimmer, and an ATS. but I do have a fuge that's working well based on the growth and hitherto a light feeding regime.
 Granted, knowing where it'll come from in the first place is a good place to start so if I can minimise the input, then maybe natural/biological filtration will keep it down

ajm83

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Reply #1

Hey buddy.

Yes it's feasible for a refugium to maintain low levels,  this is the basis behind the Triton method. However there is a limit to how fast the macro-algae grows so it can take a long time to sort an already high level (I think you said .26 on another thread?). 

It might make sense therefore to use Phosguard/Rowaphos to bring the level down a little quicker, then use the 'fuge to keep it low.



I want to stress though that it is normal for tanks to go through an ugly phase, my own tank is just going through this process, the sump now has diatoms and a little bit of cyano.


Regarding the source, it's possibly your liverock.  Phosphate naturally binds to calcium carbonate (liverock).  There is no need to get rid of the rock,  it will reach equilibrium with the water after a while and stop releasing phosphate. Again I want to emphasise that this is perfectly normal for used rock! At this stage there is no need for drastic action, just monitor the situation.  If it does not improve naturally there are things that can be done to help it along.

If you want to prove that the live rock is the source, make up a bucket of new salt water, test that the level is zero.  Then remove a bit of live rock from the tank, leave it in the bucket for a week or two and check the phosphate level in the water.


Regarding the 'diatoms', are you saying they come back after being removed (e.g. wiped away with kitchen paper)?
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semiroundel

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Reply #2

Hey buddy.

Yes it's feasible for a refugium to maintain low levels,  this is the basis behind the Triton method. However there is a limit to how fast the macro-algae grows so it can take a long time to sort an already high level (I think you said .26 on another thread?). 

It might make sense therefore to use Phosguard/Rowaphos to bring the level down a little quicker, then use the 'fuge to keep it low.



I want to stress though that it is normal for tanks to go through an ugly phase, my own tank is just going through this process, the sump now has diatoms and a little bit of cyano.


Regarding the source, it's possibly your liverock.  Phosphate naturally binds to calcium carbonate (liverock).  There is no need to get rid of the rock,  it will reach equilibrium with the water after a while and stop releasing phosphate. Again I want to emphasise that this is perfectly normal for used rock! At this stage there is no need for drastic action, just monitor the situation.  If it does not improve naturally there are things that can be done to help it along.

If you want to prove that the live rock is the source, make up a bucket of new salt water, test that the level is zero.  Then remove a bit of live rock from the tank, leave it in the bucket for a week or two and check the phosphate level in the water.


Regarding the 'diatoms', are you saying they come back after being removed (e.g. wiped away with kitchen paper)?
@ajm83, I haven't actuially wiped any away, so I don't know.
Regarding the liverock, you may or may not remember that this is the same liverock that has been in the DT since 1996, so any amount of stuff could've leached into it.
In fairness though, I remember back in the day, it was considered to not be very porous rock, so I wonder how much could've actually permeated the rock itself.
However, I did learn some useful info from youtube vids:
 Seachem Phosguard is an aluminium oxide based remover of phosphate, and typically removes phosphate very quickly so is regarded as too severe for use around corals as the sudden drop can make them go into shock, it's exhausted after about 5 days.
GFO as in Rowaphos, is slower to remove phosphate and is more suited to a longer maintenance regime and when corals are present, this once levels are low is exhausted after up to 3 months.
The former easy to deploy in a sock, the latter in a reactor so it tumbles. I will start with more Phosguard and then move to Rowaphos later
If I've got any of this wrong please let me know.

ajm83

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Reply #3

👍🏻

All sounds right, aside from I think the phosphate only sticks to the surfaces. Do give the Phosguard a good rinse in RO water before adding it to the tank as the dust is not good for some stuff.

I expect with that level of phosphate it will take a while to come off the rock. See how you get on with the Phosguard, if it doesn't do the job then once you've got your skimmer you can try one of the more hardcore phosphate removers.

Try wiping the 'diatoms' away or put a snail on it and see if it eats it!
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