Odd test results

[robert]

Personally, I wouldn't get LC anywhere near the main display or sump for that matter. If I did use it I would set up a completely separate reaction chamber in which to drip the LC and catch all precipitates.

 

[tampasnooker]

Robert - is that just being cautious or have you had/heard of bad results?
LPS - thanks for the link. I'll go through it later. I'm supposed to be painting my new fishroom today...

 

[tampasnooker]

I'm still procrastinating about painting so I read the article on Lanthanum. It seems that removing the LaPO4 before it settles on acrylic or rocks is a key. Skimmers and fine mechanical filters are best. In this tank, one of the drains goes directly into the skimmer. I wonder if I could make a VERY dilute solution and experiment with having him manually dose 1ml a day into that overflow so it goes through a skimmer and then rig a floss filter.

Now that I am writing this, I wonder if part of the issue is that there is too much flow through the skimmer. The way it was installed, half of the tank's flow goes through it. Perhaps there is not enough contact time in the skimmer for optimum efficiency? I think that I should suggest replumbing that drain to reduce water flow through the skimmer and see if I can get some more goo out of it.

 

[robert]

precipitation concerns only - I've used it in the past - nothing seemed adversely affected in my tank.

 

[lpslover]

I guess it depends what the skimmer is rated to take. If the skimmer is big enough, that much flow may not be a problem. As far as the precipitate, I split the total dose into three and dose immediately before the mechanical filtration, one third at a time over the course of an hour, pouring slowly so that the water can mix with it (20 minutes between doses.) Haven't had an issue. I guess I'd be wary of dumping it into the skimmer. Precipitate could theoretically gum up the skimmer, and skimmers are a lot harder to clean than filter socks or pads.

 

[tampasnooker]

I haven't been able to do much testing on this system until recently and thought I'd update the thread since I now have a second FOWLR that has PO4 soaring due to frozen shrimp. Here's a couple tests I ran with interesting results.

Strontium tested in the good range at 10-16 with a Salifert kit (expired 2010 though - it's what I had)

Today I pulled 3 gal from the tank and added 1 ml of Lanthanum Chloride from my local pool store. No real visible results in the white bucket. I added 5 ml more to the bucket and it turned to milk pretty quickly. I let it sit for an hour onsite then ran a P test - still over range with the Hanna checker but it did take a bit longer to turn dark blue. I'll let the solution sit over night and test it tomorrow once the Lanthanum Phosphate settles out. That should help with determining if P readings are true or if something is causing interference.

I'm still getting readings of 560+ on Ca and P overrange >2.5ppm on the Hanna, despite no addition of Ca. I have been adding Alk to let the leathers consume some. The 'nems are jammin, so are shrooms, z's and p's. I had some attrition on frogspawns but I also caught the vlamingi sampling. The two remaining heads are doing surprisingly well for the P levels. Algae growth is minimal.

Here's where the issue gets interesting. Another customer was concerned about losing an eel so I decided to do some additional testing for him. Since his is a FOLWL with a huge 'fuge full of grape caleurpa, I quit testing P a long time ago. Always 0. Well, the P reading was suddenly off the chart. I tested his RO - 0.00, then I asked him about food. Shrimp from Sams Club and Publix were recently added. Same preservatives (Sodium Tripolyphosphate and Sodium Bisulfite as preservatives). I don't know what Sodium Tripolyphosphate is but my limited Latin translates as Triple Multi Phosphate - or in other words - lots of it. Interestingly, when I went to demonstrate this to the customer, I had some shrimp thawing in tank water. Remember the tank water was >2.5, so you'd expect the thaw water to be much higher. .54 was the reading. I am completely baffled. The only conclusion I come to is that the preservatives are adding a lot of P to the water, but where did it go in the test from the thaw water? And why can't I get rid of it after ceasing the use of shrimp.

For anyone who missed it earlier, mass use of GFO and huge water changes have had nil effect on the Ca and P readings.

 

[robert]

"I am completely baffled. The only conclusion I come to is that the preservatives are adding a lot of P to the water, but where did it go in the test from the thaw water?"

Its not on the shrimp - its in the shrimp.

Shrimp are pretty high in phosphate even before being treated. There are many methods of treating - the predictable way is vacuum tumbling - but the net result of all of the processing methods is the phosphate is drawn into the flesh of the shrimp - its not on the surface. Any sodium tripolyphosphate on the surface is rinsed away - its not readily soluble in saltwater anyway. I'm guessing that even if your soak water is clean - the phosphate is still in the tissue of the shrimp.

The net result is that the excess phosphate is released after digestion.

 

[mcarroll]

Here's the thing...phosphates really do not come from nowhere. 2.5ppm in a 300g system doesn't come from the juice around the shrimp.

With nutrient levels in the water column that high there has to be a huge pile of poop hiding somewhere (or lots of "somewheres") in this tank. If the tank is significantly more than a year old, there is a high likelihood of this IME. Poke around under the rocks especially, but anywhere there's more than an inch of substrate. If anything tan or darker comes up (very likely even in a well cared for tank) you have found at least part of the problem and you can start there for your "fix". (Gravel vacuum, or siphon the substrate all out.) If you look comprehensively and there are no nutrient caches in the display or elsewhere in the system (any place there's a sand bed or mechanical filtration of any sort), then you can really look with suspicion on your test results. Get a PO4 reference solution for your meter, for example. Take a sample of tank water to one or two LFS's to get a second opinion on the actual test results.

FWIW, you don't indicate any other symptom of high nutrients other than test results.....this makes the results suspicious to me even on the surface. Algae and/or cyano should be having a heyday. There should be other signs. Ideally these are what should have led you to testing...know what I mean?

BTW, have you checked the source water? RODI actually functioning as expected? E.g. An RO membrane in backward or only partially seated will blow out your DI phase in a hurry and let lots of nasties through. Incorrect DI cart (usually on accident or due to a mislabelling) can also bring on a condition like this. Any of those may not be obvious at first glance either. Check your TDS or the PO4 (or even pH) of your tap and makeup water. (Sorry if I missed this having been done already.)

-Matt

P.S. Is there any reason why food with preservatives is being used in the first place? Regardless of impact to PO4 I would avoid this. Also, were any new rocks (or critters) added to the system in the Spring/early Summer when or before you started noticing this?

 

[robert]

Whoa - I just read your post again and now I see the mystery -
The shrimp were thawing in the tank water and the phosphate in the thaw water dropped! - Now that's cool....

I'm gonna get me a pound and a half of shrimp and stuff them in a reactor. Who needs GFO!

I think the shrimp flesh may have bound the phosphate in the thaw water -
The problem with phosphates is that there are so many forms of the stuff - not all biologically available - and it complexes with so many of the ions in the tank. At elevated pH it can bind with ammonia and mag and precipitate out as struvite - MAP (magnisium-ammonium-phosphate) and then disassociate again as pH drops. This usually happens in anaerobic areas.

If the test is good - and it probably is - then it may be picking up a non-biologically available form. If water changes don't cut the levels - then as matt suggests, you've got a robust source in the tank. If the pH has been kept elevated - the substrate is bound to be full of phosphate.

 

[beaslbob]

If your nitrates are unmeasureable you might want to bump them up to 5ppm.

the idea is the algae/macros may have become nitrate starved and with faster growth will bring down the phosphates.

Again for elevated calcium and depressed pH try adding some baking soda. But no much.


my .02

 

[tampasnooker]

Thanks guys.

Bob - sounds like Redfield ratio thinking. I"ll look into that.

Robert - run shrimp in the reactor for 5 min prior to feeding, eh? Should get the fish nice and hungry.

Matt - we can vacuum the whole tank with 10 gal. Substrate is sugar sand - oolitic sand - fine aragonite about 1-3" deep, depending where the fish piled it up that week. The waste water is pretty grey - not brown like nutrient laden sand. Algae growth is minimal, in fact I just saw the first green slime algae in a small patch which I ususally associate with very low nutrients. RO water tests fine on a regular basis for TDS and P. There are 3 tanks in the office. We don't bother with much chem on the big FOWLR besides alk - no algae = happy. There is also a 55 mixed reef with normal and manageable P, Ca, Alk levels. The 300 reef is the enigma.

I switched to shrimp from silversides that he had been used for the first few years he had this tank. I figured the P was from the fish - not like silversides are the cleanest food... Perhaps it's time to forgo the grocery store and visit the fish market for foods for the big guys. As a fisherman, I have access to scaled sardines locally that we use for bait, but I've run into P issues using them in the past, too. Since 'nems are so happy, maybe I should just turn this one into a RBTA / maxi-mini garden and leave well enough alone...

 

[tampasnooker]

Since we're investigating feeding, anyone have any thoughts about foods that have a higher N-P ratio when they come out the back end? Most of the foods I've been using are low on the food chain - close to phyto consumers which you'd think are higher in P in the flesh. I'm pretty stingy about sharing my redfish or the day's catch with someone else's aquarium... I wonder how the bits that don't get filleted would work as an aquarium food - guts, belly, etc from a predator that's a level up on the foodchain compared with fish that eat phyto and other planktons.