Phosphate removal

[drukkosz]

I am trying to fight my phosphate level to lowest possible.
Right now my DT has phosphate from 0.09 to 0.06 (hanna) and i cannot get it lower.

I do run GFO in BRS dual reactor with carbon in second chamber, but when i tested my water coming from it, it reads 0.05???? ANy idea why? last week i replaced my GFO because it was reading 0.06 but this didnt really do much.

any suggestions what else i can do? I feed my fish once a day or none sometimes and lately and replace 20% weekly water with 0 RODI water.

 

[Randy Holmes-Farley]

The GFO is likely depleted and needs to be replaced. Using more may also help you bring down phosphate.

 

[drukkosz]

like I mention before, i did just replace my GFO and is still reading 0.05. Also i did use BRS calculator and put 1.5 cup of GFO in my reactor.

thanks

 

[tmz]

I have not had much luck keeping the flow right with the brs dual reactor,paticularly if you are using granulated gfo. The TLF reactor with HC BRS gfo works for me. More gfo with good flow through it and changes as needed will reduce it. I run rox 8 arbon separately.

It is also possible your rocks and substrate will leach back PO4 for weeks even when you keep the level of it in the water low.

 

[arkaeus]

Do you have the new BRS containers for the reactor? I find they work much better

 

[Randy Holmes-Farley]

like I mention before, i did just replace my GFO and is still reading 0.05. Also i did use BRS calculator and put 1.5 cup of GFO in my reactor.

thanks

You didn't say how long before you took a measurement. I thought it might have been a few days, in which time it could easily be depleted, and if you have truly elevated phosphate (and the reactor is actually exposing water well to the GFO), then adding more and changing it more often can be a good idea.

Are you using a Hanna 713? If so, the high level on uncertainty makes it hard to know what's going on based on phosphate measurements.

 

[kissman]

i was running double the amount of GFO and I was still getting some PO4 coming out, I slowed the water flow down and didn't worry about the boiling much because I was changing it out every 2 weeks anyway. worked for me, never saw 0 coming out but i did beat the cyano in my tank

 

[drukkosz]

It is also possible your rocks and substrate will leach back PO4 for weeks even when you keep the level of it in the water low.

My tank is 1.5 years old and there are no new rocks added

Do you have the new BRS containers for the reactor? I find they work much better

Yes i upgraded containers 2 months ago

You didn't say how long before you took a measurement. I thought it might have been a few days, in which time it could easily be depleted, and if you have truly elevated phosphate (and the reactor is actually exposing water well to the GFO), then adding more and changing it more often can be a good idea.

Are you using a Hanna 713? If so, the high level on uncertainty makes it hard to know what's going on based on phosphate measurements.

Yes Hanna 713, i didnt really know about the other one till i bought it.
I took measurement 2 days after replacing GFO.

i was running double the amount of GFO and I was still getting some PO4 coming out, I slowed the water flow down and didn't worry about the boiling much because I was changing it out every 2 weeks anyway. worked for me, never saw 0 coming out but i did beat the cyano in my tank

I am playing with a flow going thrugh reactor as well and right now its slow. what i dont understand is why after replacing 20% water every week phosphates wont reduce. I cannot figure out what is producing it. I know its not food because i feed one a day tiny portion.

Thank you all for your replays

 

[DHyslop]

My tank is 1.5 years old and there are no new rocks

Have you been testing phosphates the entire time? It's possible that you've had elevated levels and/or phosphate trapped in the rock for the entire time. Without seeing pictures of the tank, it's also possible that your aquascape has dead zones or areas that can't be cleaned and after a year enough rotting detritus has built up in there to cause problems. Where did the rock come from? The live rock tanks at most LFS are nutrient pits.

Keep in mind it's entirely possible to have a tank that has very high nutrient levels without any outward symptoms. This can go on for years and then suddenly one day for no reason you have cyanobacteria or hair algae. Kind of like the way someone can smoke for 40 years and think everything's fine because they haven't gotten cancer yet.

I just picked up a new client with nitrate around 50 mg/l and phosphate 0.61 mg/l. No sign of nuisance algae! But we're going to do a full renovation of the tank because I can't expect it to stay that way.

 

[roblk]

Check your RODI phosphate level, 0 TDS doesn't mean .00 phosphate level I was having the same problem with my tank .09 po4 running GFO and 20% water changes without lowering p04 level measured RODI water and measured .09 ppm. Changed cartridges and RODI water now measures .02 ppm

 

[Randy Holmes-Farley]

i was running double the amount of GFO and I was still getting some PO4 coming out, I slowed the water flow down and didn't worry about the boiling much because I was changing it out every 2 weeks anyway. worked for me, never saw 0 coming out but i did beat the cyano in my tank

FWIW, slowing flow down isn't necessarily useful, even if it does appear to lower the effluent phosphate more.

For example, these different scenarios are removing the exact same amount of phosphate from the aquarium:

Tank at 0.1 ppm phosphate

flow 1 gal/min phos 0.09 ppm
flow 0.5 gal/min phos 0.08 ppm
flow 0.25 gal/min phos 0.06 ppm
flow 0.125 gal/min phos 0.02 ppm

 

[Randy Holmes-Farley]

Check your RODI phosphate level, 0 TDS doesn't mean .00 phosphate level I was having the same problem with my tank .09 po4 running GFO and 20% water changes without lowering p04 level measured RODI water and measured .09 ppm. Changed cartridges and RODI water now measures .02 ppm

FWIW, I do not think that anyone needs to chase after phosphate levels in 0 ppm TDS water because either 0.09 or 0.02 ppm phosphate in that water (assuming either is accurate) is not significant relative to the phosphate most people feed in foods.

I discuss it here:

Phosphate and Food
http://www.advancedaquarist.com/2012/3/chemistry

from it:

Comparison of Food Sources of Phosphate to Other Sources
What about other sources of phosphate, like the "crappy" RO/DI water containing 0.05 ppm phosphate? A similar analysis will show it equally unimportant relative to foods.

Let's assume that the aquarist in question adds 1% of the total tank volume each day with RO/DI to replace evaporation. Simple math shows that the 0.05 ppm in the RO/DI becomes 0.0005 ppm added each day to the phosphate concentration in the aquarium. That dilution step is critical, taking a scary number like 0.05 ppm down to an almost meaningless 0.0005 ppm daily addition. Since that 0.0005 ppm is 40-600 times lower than the amount added each day in foods (Table 4), it does not seem worthy of the angst many aquarists put on such measurements. That said, tap water could have as much as 5 ppm phosphate, and that value could then become a dominating source of phosphate and would be quite problematic. Purifying tap water is important for this and many other reasons.

 

[Randy Holmes-Farley]

Yes Hanna 713, i didnt really know about the other one till i bought it.
I took measurement 2 days after replacing GFO.

Then I'd say that you are really unable to say too much about the in and out levels in terms of the reactor.

The tank level (reading 0.06 ppm) is somewhere between 0.02 ppm and 0.10 ppm, and the output from the reactor (reading 0.05 ppm) is somewhere between 0.01 ppm and 0.09 ppm.

 

[kissman]

FWIW, slowing flow down isn't necessarily useful, even if it does appear to lower the effluent phosphate more.

For example, these different scenarios are removing the exact same amount of phosphate from the aquarium:

Tank at 0.1 ppm phosphate

flow 1 gal/min phos 0.09 ppm
flow 0.5 gal/min phos 0.08 ppm
flow 0.25 gal/min phos 0.06 ppm
flow 0.125 gal/min phos 0.02 ppm

I was thinking that slowing the flow through the reactor would allow more contact time with gfo and lower phosphates

 

[roblk]

FWIW, I do not think that anyone needs to chase after phosphate levels in 0 ppm TDS water because either 0.09 or 0.02 ppm phosphate in that water (assuming either is accurate) is not significant relative to the phosphate most people feed in foods.

Good point, Hanna Instruments HI713 accuracy is only + or - 0.04 ppm.

 

[Randy Holmes-Farley]

I was thinking that slowing the flow through the reactor would allow more contact time with gfo and lower phosphates

In a continuous circulating system system, if there is any effect of increased contact time, it is actually going to work against you, not for you.

This is a different scenario than a single pass system where I agree slowest is best.

Think of it this way. The more phosphate in the water, the more phosphate binds to GFO.

If you have fast flow, the concentration doesn't drop much in the reactor, and so the GFO is always in contact with higher phosphate water and always is maxed out in terms of the rate that phosphate is binding.

If the flow is slowed, the levels drop more in the reactor, and so the rate of phosphate binding to the GFO declines.

That said, there may be other important reasons for not having flow too high, such as breaking particles apart, pushing GFO out of the reactor, channeling through packed beds, etc.

 

[FNDsalt]

Yes Hanna 713, i didnt really know about the other one till i bought it.
I took measurement 2 days after replacing GFO.

Is this referencing the low range phosphate checker? Or is this in reference to the 713 vs. the 717 reagent?

 

[Randy Holmes-Farley]

Yes, he means compared the the 736 which has (or at least claims) better accuracy.

 

[ken6217]

Maybe it's your carbon.
Ken

 

[Randy Holmes-Farley]

FWIW, I do not think that GAC is a significant source of phosphate for most reefs (unless you are using something not intended for aqauria).

I discuss that in the article I linked above. From it:


The same sort of calculation applies to analyzing other phosphate issues, such as the GAC in scenario three. The issue of finding "high" phosphate in GAC soaked in fresh water was frequently quoted as a reason to use one or the other brand of GAC, and probably still is. But simple analysis as shown above for the food rinsing puts the lie to this being a big problem.

One needs to consider how much GAC one will really use in the aquarium and how often it is added in order to interpret how important the added phosphate is. A typical recommendation might be 1 cup of GAC per 100 gallons of aquarium water, and to change it in 4-6 weeks. Let's assume we detect 0.5 ppm phosphate when a teaspoon is placed in a cup of water, and we get scared by the dark blue color during the test. Is this reasonable? That 0.5 ppm from a teaspoon in a cup of water translates to 0.015 ppm phosphate when a cup is used in 100 gallons.

That 0.015 ppm may be significant, being a typical target concentration level for reef aquaria and amounting to about half to a twentieth of the amount added daily in foods, but remember, it is used for 4-6 weeks. During those 4-6 weeks before the next replacement, foods add 50-700 times as much phosphate. So while it is not unreasonable to look for another brand of GAC, to blame phosphate or algae issues in the aquarium on its use would stretch credibility because it is a very tiny portion of the total phosphate being added.