Reactor Effluent & Phosphate

[FishDad2]

Randy,

I'm trying to track down the source of phosphate in my tank so I've tested my RODI water and salt mix using the Salifert test kit, and they both showed nothing.

The only other things I add to the tank are food and the dissolved materials in the effluent from the calcium reactor.

As regards the food, I've been in the habit of pouring out the juice and unabsorbed additives (VitaChem, Selcon, etc.) from the frozen food before feeding...and I leave the pumps off long enough that the vast majority of the food is eaten by the fish. Only the smallest pieces don't get eaten, but there's not a lot of that and I have quite a few crabs, etc. to clean up the little that doesn't get eaten by the fish or taken in by a filter feeder. And of late, I've actually been rinsing it off with RODI water beofre feeding the tank, as opposed to just pouring off the excess juice, etc.

The foods themselves are commercially prepared fish foods...Prime Reef from Ocean Nutrition, Brine and Mysis Shrimp from San Francisco Bay Brand. Additives, which I rotate from day to day for variety, include Selcon, VitaChem, Marine C and Marine Zoe.

Given the measures taken with the food, I don't think it's the source of phosphates...at least not one that's causing the bulk of the accumulation.

So that leaves the reactor effluent as the main "additive" to be tested. Having said that, I tested it using the same Salifert kit and got a reading of .50 ppm…the tank tests at .15 - .25 ppm. Note too that the reading for the tank was .50 ppm prior to my starting to use PhosGuard to bring the levels down...I did not think to test the reactor at that time.

Woo hoo, I found my source (or at least a big contributor) so now all I need is a “better� reactor media and/or a way to remove the phosphate from the effluent before it gets in tank…or so I thought. As I’ve now learned though, it seems that the high alkalinity of the effluent is likely skewing the results higher than they really are. One person suggested diluting the effluent with RODI water until the dKH drops to ~8.0 and then test. That certainly would reduce/eliminate interference from the high dKH, but at the same time, would it not also dilute my test results and therein render them equally inaccurate?

So, the big question is, how do I get an accurate reading of phosphate levels in the reactor effluent (recognizing that “accurate� is a relative thing using the typical home aquarist test kits of course)? I want to track down the source and address the problem, but if I’m not sure how to properly test the effluent and get a reading that I can reasonably compare with the reading I get for the tank as a whole.

Sorry for all the extra details about the food and all that, but I figured it's better to be thorough, as you may have other thoughts or suggestions as to sources and remedies. And towards that end, the only other source I can imagine (aside from the live rock itself, and I shudder to think of the implications of the rock being a significant source) is the substrate...Nature’s Ocean - Pink Samoa. In theory it’s phosphate-free, but perhaps you’ve heard of others having phosphate problems with it?

You assistance is appreciated as always.

Thanks,
Chris

[Randy Holmes-Farley]

Given the measures taken with the food, I don't think it's the source of phosphates...at least not one that's causing the bulk of the accumulation.

All foods contain phosphate. It is not something that can just be rinsed off, but is an integral part of proteins and many other biomolecules. I wouldn't assume you need need to look for another source. Eaten food contains phosphate that is then excreted.

FWIW, phosphate kits do not work well in high alkalinity fluids like reactor effluent. Dilute it to an alkalinity of about 10 dKH if you want to make it more accurate. If you dilute by a factor of 2, then just multiply the answer by a factor of 2. Same if you dilute by a factor of 4, multiply the answer by 4. So it may be a contributor, but it also may not be significant.

These articles may be useful:

Phosphorus: Algae’s Best Friend
http://www.advancedaquarist.com/issues/sept2002/chem.htm


Iron Oxide Hydroxide (GFO) Phosphate Binders
http://reefkeeping.com/issues/2004-11/rhf/index.htm


Aluminum and aluminum-based phosphate binders
http://www.advancedaquarist.com/issues/july2003/chem.htm

[FishDad2]

Thanks Randy...I'll do some more reading and testing.

Good to know it's as simple as dividing by the dilution factor...was concerned it was perhaps more complicated than that, as sometimes seems to be the case with certain chemical tests.

I guess since it's a 225 gallon tank (with a large sump and a refugium, so lots of water) and only few small fish (therefore small feedings), I've discounted the possibility of the food being the primary source...probably an unwise assumption as you point out.

Assuming for the moment that the reactor effluent is not a major contributor, how then can I test the food as a source? Is there an easy way for me to do that at home, particularly as I'm not a chemist nor do I have access to lab...not that I'd know what to do with access if I had it.

Thanks again,
Chris

[Randy Holmes-Farley]

You can test for phosphate that easily comes offthe food, but much is incorporated into the food and cannot readily be tested for. It would not take much food at all to get to 0.25 ppm if you did not have much in the wya of phosphate export.

Is the caulerpa growing fast?

[FishDad2]

Right now I have a mix of caulerpa, cheato and red gracilaria in the refugium. The red gracliaria seems to be the best grower of them all right now. The cheato has a healthy look to it but hasn't grown much (I only added it a week ago though, so I need to give it some time), while the caulerpa's growing a bit but looks to be the weakling of the bunch right now.

The effluent is setup to trip on the upstream side of the refugium as well in the hope that the algae will take up some of the phosphate and excess CO2 before it makes its way back to the main tank.

The refugium light is being run counter to the tank...a PC fixture using the 10K/Actinic bulb that came with it. I have a 6700K bulb coming this week though, in the hopes that the lower color temp improves the growth rate.

I also diluted the effluent and retested last night as suggested. At dKH 9.8, the phosphates in the effluent tested at ~.60 ppm. At the same time, the tank phosphate is down to ~.15 ppm with a fresh batch of PhosGuard installed on Sunday afternoon.

[Randy Holmes-Farley]

while the caulerpa's growing a bit but looks to be the weakling of the bunch right now.


Perhaps the Caulerpa needs some supplemental iron to grow optimally. Many folks have found it grows faster with iron dosing.

I also diluted the effluent and retested last night as suggested. At dKH 9.8, the phosphates in the effluent tested at ~.60 ppm. At the same time, the tank phosphate is down to ~.15 ppm with a fresh batch of PhosGuard installed on Sunday afternoon.

That sounds good, although I'm not a fan of phosguard due to released aluminum. I prefer the iron based binders.

That said, maybe it is appropriate to try a diffewrent media int eh reactor to see if that helps. I've never heard of specific phospahte comments about the one that you are using.

These articles may be useful:

Greg Hillers analysis of limestone media for CaCO3/CO2 reactors
http://www.aquariumfish.com/aquariumfish/detail.aspx?aid=1995&cid=124&search=

Calcium Reactor Substrate -- Phosphate Levels
by Greg Hiller
http://www.advancedaquarist.com/issues/april2003/short.htm

[FishDad2]

I'll look at supplementing iron...thank you. I'll also look at some other reactor medias, although the articles you pointed me to favor the use of the product I'm already using today, so... And as for the Phosguard, I've been thinking of changing anyway...just been putting it off until my supply runs out.

Of course, I greatly prefer natural removal, which is why I built the refugium in the first place. However, assuming for the moment that I can't achieve a sufficiently low phosphate level over the long-term through natural removal alone, I think I need to improve the efficiency of how I use the chemical media in my system in order to protect the display tank. Today, I have the media in a canister that's on a closed loop in the tank...so the water from the sump, which includes the high phosphate reactor effluent, must first enter the main tank before it even has a chance of being sucked into the loop and filtered through the media. That doesn't seem to be terribly efficient to me.

So, I thought of placing a canister filter on the return line from the sump to the tank and filling it with whatever chemical media I may need at any given time...carbon, phosphate remover, etc. In this way, any water passing through the sump, which includes the effluent from the calcium reactor, would be forced to travel through the chemical media before making its way back to the main tank.

The two drawbacks I can see are that the addition of the canister creates some back pressure so it'll reduce flow, and also that the presence of the filter media in the line will prevent the critters in the refugium from making their way to the main tank.

I can make up for loss of flow easily enough, but impeding the path of the critters to the main tank seems more difficult to solve...especially if I want to have the effluent first pass through the refugium in an effort to remove the phosphate naturally. Do you have any suggestions or thoughts on how to efficiently remove the phosphate before I pump it back into the tank but without blocking the critters route? My concern is that it’s something of an either/or situation...remove it naturally but impede the migration route or remove it chemically and maintain the migration route.

Any suggestions would be appreciated, as there’s something inherently disturbing to me about knowingly pumping phosphate into my tank. Not to mention that I’ve been resisting the urge to add corals until I get all the water parameters under control…you helped point me in the right direction to get the reactor tweaked and now I have alkalinity and calcium working for me, just need to clean up the phosphate and eliminate some nitrate that’s started to build up and I’ll be ready start with the corals…every day it gets harder and harder to resist!!

Thanks again!

[Randy Holmes-Farley]

Putting it in line like that may make you shut down and possibly even drain the return any time you need to swap media, etc.

I run a powered cannister off my sump, and it returns the water there after passing over carbon.