Phosphate - cause and control

[viper357]

I have put together bits and pieces of information regarding phosphate, let's discuss the causes of phosphate and also ways to control it in our aquariums.

Phosphate (PO4) is a very important parameter that needs to be kept in check in a marine aquarium. A build up of phosphate can lead to problems with nuisance algae, sometimes to such an extent that a hobbyist may very well leave the hobby due to an ongoing and seemingly never-ending battle with algae.

It is very difficult to measure phosphate accurately as there is organic and inorganic phosphate. Most test kits test the latter, which usually test low due to the algae consuming it as quickly as it is produced. Efficient skimming will reduce the organic PO4 while phosphate remover such as rowaphos will take care of inorganic PO4. One should also take into account that phosphate may reduce calcification in sps, lps and coralline algae. Caulerpa or Chaetomorpha based sumps/refugiums help to reduce phosphate and nitrate levels.

It is always better to lean towards prevention as being better than cure (get rid of the source), using RO water is a good place to start.

Let us share and discuss/debate some common causes of phosphate build up:

Low quality RO water or tap water
Overfeeding or using food that contains PO4
Carbon with phosphate content
Insufficient skimming
Insufficient filtration
Low quality salt mixes/nsw
Low ph/kh - apparently if your ph is low, the phospate that was bound to the calcium will dissolve and become soluble thereby releasing the phosphate back into the system .

 

[irie ivan]

Overfeeding or using food that contains PO4

As far as I am aware, all frozen food, or any food from animal/plant/fish origin will contain PO4.

Carbon with phosphate content

Often overlooked by hobbyists, but mentioned in every book I have ever studied. There are a few brands which is very low in PO4, think mosty the lignite or butiminous ones.

Low quality salt mixes/nsw

I doubt whether the PO4 in nsw are present at levels to make a significant impact on PO4 levels in our system. I do however believe that PO4 bound up in biomass (bacterial, microbial or microfauna) present in nsw added to a system can do its bit towards increasing PO4.

Insufficient skimming
Insufficient filtration

Definitely a major (if not THE major) contributing factor towards elevated PO4 levels. Effective filtration will remove uneaten food, particulates before it can decompose into things like PO4 and NO3.

Low ph/kh - apparently if your ph is low, the phospate that was bound to the calcium will dissolve and become soluble thereby releasing the phosphate back into the system

Whether it is because of lowered pH or simply the rock or substrate bound PO4 levels tryeing to reach equilibrium with the water column levels I am not sure, but PO4 originating from our substrate is a reality.

 

[Alfie]

Ivan, what brand of carbon would you recommend?

 

[palmerc]

It is a good idea to rinse any activated carbon well in lots of RO water before use. You can remove practically all the phosphates this way.

Try it and test the RO water afterwards - see how much there is

 

[Vernon]

Nice topic!! Most newbie phosphate problems seem to come from under skimming and detris build up...

 

[palmerc]

I reckon the number one cause of phophate problems is overfeeding.

Coupled with insufficient nutrient removal thsi will cause problems.

 

[irie ivan]

Seachem matrix carbon

 

[Alfie]

I currently use AM. How do you rate this?

 

[sunburst]

It is a good idea to rinse any activated carbon well in lots of RO water before use. You can remove practically all the phosphates this way.

Try it and test the RO water afterwards - see how much there is

Makes me wonder...if rinsing in ro water can remove phos then why dont supliers do their bit and market a phos light product. Like low fat and sugar free

 

[palmerc]

They work with ton quantities, probably a bit difficult to do for most companies.

I do this on a small scale so it's not a problem, just wash it well, rinse and leave it in the sun to dry. Phosphate afterwards is virtually undetectable.

 

[palmerc]

I don't know if you've ever noticed, but most suppliers recommend on the label to rinse the carbon well before use. This is supposedly to remove fines, but I suspect it also serves as a phosphate reduction method - so they get the reefers to do their work for them.

 

[sunburst]

Great selling point. Is it safe to say no carbon is phos free

 

[irie ivan]

Good question........... One which will only be answered if independant ests are conducted. I know some of the butiminous carbon suppliers claim theirs is PO4 free.
A reputable company like sachem states on their lable that there is no carbon which is PO4 free. As far as I remember, two little fishies also claims their carbon (lignite based) does not leach PO4.

To err on the safe side, I prefer using a product such as seachem PO4 guard, which is a blend of carbon and PO4 remover. Really works well.

I am not a fan of Aqua Medic at all, so cannot give an objective opinion on their products. I have used it in the past, and it did a job, but nothing in comparison to the Seachem stuff, which outlasts the AM stuff volume for volume. Whether this is due to the spherical shape (and therefor resistance to clogging) of the Seachem or the composition (origin of the carbon) I am not sure.

 

[sunburst]

I have used it in the past, and it did a job, but nothing in comparison to the Seachem stuff, which outlasts the AM stuff volume for volume.

I change my carbon every two weeks because i am told to. How do you know, besides perhaps visually, that carbon needs replacing

 

[palmerc]

Great selling point. Is it safe to say no carbon is phos free

All carbon is derived from organic matter so will contain phosphates. However some carbons may have been treated to make them virtually phosphate free.

Another tip is not to exceed recommended supplier treat rates as you may increase phosphate levels unnecessarily, even with an excellent quality carbon.

As an example say a carbon had 10mg/kg phosphate (a good number) and you use 1 kg on a small tank say 100l. You will then add 10ppm of phosphate to 100litres of water which is 0.1ppm, change thi severy secodn week and you very quickly start getting to levels where it is problematic esp if you are introducing other phosphate sources like food.

But use the same 1 kg on a 1000 litre system and the effect is minimal. I usually work on a treat rate of around 30-50g (about 50-100ml) of carbon per 100litres of water.

Thsi is more than adequate to treat the water yet usually good enough to minimise effects of a fairly decent carbon. With a poor quality carbon you will still get problems at this treat rate.

 

[irie ivan]

I change my carbon every two weeks because i am told to. How do you know, besides perhaps visually, that carbon needs replacing

The old yellow line on paper test.
Draw a yellow line on a white piece on platic (use a permanent marker) and dip in tank. Hold at back of tank and if you cannot see the line, time to change. Thats the only way I know, but to be honest, I seldom do this. Just change as refularly as I can afford

 

[Midasblenny]

Pure Reef Phosphate Remover eliminates phosphates from water with no detriment to fish or coral, personally i dose once a month.

 

[Copperband]

Pure Reef Phosphate Remover eliminates phosphates from water with no detriment to fish or coral, personally i dose once a month.

Robin can you overdose on this one?

 

[Midasblenny]

Robin can you overdose on this one?

Provided a dose of kh buffer is added before and after dosing no one cant overdose as the lanthanum(chemical used to bind the phosphate) will in the presence of no phosphate bind to carbonate. In the presence of phosphate lanthanum does however have a greater affinity for phosphate.

 

[jacquesb]

Hi all - one MAJOR oversight, which I have rudely discovered, and I think is MOSTLY overlooked, is that a LOT of the sources of phosphates in a lot of reef tanks, are "hidden detritus build-up".... For example, INSIDE of the live rock, between the different pieces of live rock, etc...

I think that even though it has been discussed MANY times, and I also "found out by decent debates", that one ACTUALLY need to have strong flow THROUGH one's live rock, and behind/below one's live rock. That this is not an option, BUT imperative to have!

Otherwise this would most likely end up causing major head-aches for many reefers in the long run (and perhaps even in the short run - IF the live rock contained this "crap" even before the reefers placed the live rock into their systems...

I don't think that any form of standard "curing" of the live rock, would remove "locked"/hidden detritus within the live rock.