High Phosphate

[imatrout]

I have phosphate levels in my tank that re nearly 10 ppm. This was caused by a bad bag (or two) of eco-complete. My tank is and has been algae free, but some plants are stunted (Blyxa) while others grow like crazy (Hydros). No wonder Hydorphila is a noxious weed in our phosphate laden public waterways!

I have kept my NO3 relatively high as a balancing act (20 -25 ppm). All other macros and micros are dosed to spec and i have a healthy amount of CO2 at 38 ppm.

Has anybody used a product like Phos-Buster from CaribSea? Isuspect my problems are related to the phosphate, but don't want to tear the tank down. Any other ideas for removing phosphate would be appreciated. My thinking is that I could use a remover to accelerate the the reduction of PO4 that is in the substrate. I'll have to use it for awhile until it all leaches out.

 

[Tom Barr]

Re: High Phosphate

High PO4 is not the issue.
What does high PO4 potentially do when added to buffers?

Gives you a false positive for CO2...........

Blyxa is more sensitive to lower amounts of CO2 than Hygro is certainly.

Regards,
Tom Barr

 

[imatrout]

Re: High Phosphate

High PO4 is not the issue.

Regards,
Tom Barr

Then what do you think the issue is? PO4 at 10 ppm seems really high. Are there any other side effects of the PO4?

 

[colonel]

Re: High Phosphate

I think what Tom is saying, is that the high PO4 isnt whats causing the stunting of your Blyxa... that its more likely an issue of the PO4 throwing off your CO2 reading, and that the issuse probably has more to do with you having less CO2 than you think.

Maybe try to increase that a bit and see if it doesnt help. But yes 10 ppm PO4 is high.... and as far as your question about using something to help lower it I dont really know.... as I have never used any of those products before

 

[imatrout]

Re: High Phosphate

Thanks colonel!

How much effect does PO4 have on the CO2? Is there any way to calculate the effect?

 

[PeterGwee]

Re: High Phosphate

Thanks colonel!

How much effect does PO4 have on the CO2? Is there any way to calculate the effect?

It will skew your KH reading making the actual CO2 level higher than expected. Get a sample of your tankwater and then let it sit for 24hrs before measuring the pH/KH. If the CO2 level is higher than normal other than 3-4ppm, you would know how much error it has induced. Substract that amount from all your readings taken and you should get a value close enough although still not perfect.

Regards
Peter Gwee

 

[Tom Barr]

Re: High Phosphate

To lower PO4, simply do large water changes.

That will reduce the PO4 down considerably, over time the PO4 effect will be greatly reduced.

You can also vacuum the gravel every so often.
It's much like an enriched gravel since it has the PO4, when you get about to 5ppm and beyond, it starts to have some effect on the KH readings, 10-20ppm etc will toss the readings off by about .2 pH units or a .5 to 1 KH unit.
Maybe more, I'm not enitrely sure but they do use PO4 based acids to lower pH in several products and these defintiely throw the CO2 off by causing the pH to be lower, but the CO2 is still the same.

Regards,
Tom Barr

 

[VaughnH]

Re: High Phosphate

The easy way to "measure" CO2 and get around the high phosphate or tannin problems is to take a sample of the tank water, let it sit overnight, measure the PH. Compare that to the PH of the water in the tank at least a couple of hours after the CO2 is on. If you have a drop of about 1.0 in PH, you have around 30-40 ppm CO2, right where you want to be.

 

[imatrout]

Re: High Phosphate

Thanks all. I get it now. Let the water sit so the CO2 dissapates then test and compare the PH to water currently at saturation levels. The delta is the amout I am adding regardless of what the CO2 chart says.

 

[Tom Barr]

Re: High Phosphate

Yes, this is an old back door method I use to use with peat laden water for finding CO2.

People use to think I was clever back then

Regards,
Tom Barr

 

[imatrout]

Re: High Phosphate

Okay. I tested the CO2 using this method and the results were:

Aged water PH = 7.6+
Water at saturation = 6.6

I assume that a full point drop implies I have between 30 - 40 ppm of CO2 correct?

That said, why are some plants like the Blyxa stagnant and the najean deformed while all other plants grow like crazy. I have zero algae for nearly 6 months (fingers crossed)

KH = 8.5
GH = 15
NO3 = 20 -25 ppm
PO4 = 10 ppm (the suspected problem)
CO2 = 30 - 40 ppm (aged water method)
I dose Micros and iron using Seachem Flourish and Flourish Iron be the directions

The tank is a 150 gal with discus in it. (see May TFH pg. 56). I dose weekly:

1.5 tsp of KNO3
1 tsp of K2SO4
.25 tsp of KH2PO4 (I know this is low, but I add so little because PO4 is already at 10 PPM.

I did question the difference between organic and inorganic PO4 as in: Maybe the PO4 caused by the Eco-complete is not as available to the plants as the PO4 I add with the KH2PO4? Any thoughts?

 

[PeterGwee]

Re: High Phosphate

Add enough PO4 and ignore the test kit for a while. See if it the plants improve after 1-3 weeks time. Don't trust the kits too much. How much light do you have over the tank?

Regards
Peter Gwee

 

[Tom Barr]

Re: High Phosphate

If it's a full blown discus tank, try adding 1 teaspoon of KNO3 instead of 1.5.
Back off the K2SO4(after water change only).
Try adding TMG instead

The EC PO4 source will be inorganic, the material is inorganic, thus bioavailable.

Large water changes should correct the issue.

Regards,
Tom Barr

 

[imatrout]

Re: High Phosphate

Regarding lights, I have 384 watts of PC lighting over this tank (2X6700K & 2X 10000K, 96watt ea.)

As an aside, I only add the doses I posted on a weekly basis except for micros which I spread out evenly on a daily basis.

I have been doing 60% WC weekly for 6 months. The PO4 levels have fallen to a little less than 10ppm vs the 15 ppm I started with. I use a Salifert PO4 kit. Since the kit maxes out at 3 ppm, I combine 90% distilled water with 10% tank water and get a reading of slightly less than 1 ppm then multiply by 10. Is that the right way to measure it?

BTW, I'm learning a lot through this thread, especially re: CO2 degass measurement...I like!

Also Tom, why TMG versus Flourish (what about iron) and why less KNO3 in a discus tank?

 

[Tom Barr]

Re: High Phosphate

I think the method used to measure the PO4 seems fine off the top of my head. Serial dilution to get into the effective range is fine.

TMG is likely better at the KH you have.
Try it and see.

The 1.5 teaspoons per every other day or 3x a week is what I assumed you meant.

Adding 3/4-1 teaspoons 3x a week should be about right.
Most Discus folks feed their fish a lot, so there's a fair amount of N floating around.

I'd rather see you run the NO3 a bit lower to push the NH4 uptake from these food sources.

I also think the high KH is influencing the Blyxa and Rotala to some degree also.

Since it's a Discus tank, you might consider knocking the KH down by about 50%, so at 60% weekly: 45 gal of tap and 45 gal of RO water.

Or you can leave it, try the other suggestions and see if things improve.
CO2 will help to some degree, but you might be cornered with those two plant species and KH.

GH can be quite high.
Most folks here in the harder water areas do fairly well with Blyxa, but it's a weed in my soft water as it was in FL even with Onyx sand.

A KH of 4 should pose no issues for most any plant.

It's up to you how bad you want that plant, micro tennellus is an alternative that will do well. It's more weedy though.

Regards,
Tom Barr