I'll be darned...it actually worked! :)

Waterjockey · May 31, 2016

Woot!!
I have been dosing vinegar to get my nitrates and phosphates down. I began to dose potassium nitrate a little over a week ago, suspecting I was now nitrate limited as I had 0 nitrates and couldn't move phosphates any lower than .2. This morning, for the first time ever, I got 0 on the hanna low range phosphate checker! Now, nitrates have begun to rise.....I suspect this may be because I have now achieved some phosphate limiting, does that sound reasonable? My little 30 gallon mini reef is mainly lps, my goal is not to run an ultra low nutrient system, but to ultimately have a trace of nitrates and phosphates in the system.
So my course of action was to set my nitrate dosing pump to half the rate to hopefully see a slow decline in nitrate levels to 0 again. When that is achieved, slowly back my carbon dosing down till hopefully I am able to achieve a balance of minimum carbon and nitrate dosing to maintain trace nitrate and phosphate readings. Does this sound like a reasonable plan? I suspect my very old live rock is still leaching phosphates and I believe I will need to maintain carbon and I nitrate dosing for an extended number of months.
My lps have never looked as puffed up as the last week or so

(except my small Montiporia frag is showing some white around the edges, working on lowering dKh)

Cheers!

ryboy707 · May 31, 2016

I am in the same boat. I have been dosing nopox tho. What did you use to dose potassium nitrate? everybody said spectracide stump remover was the easiest to do so I went with that.

Waterjockey · May 31, 2016

ryboy707 said:
I am in the same boat. I have been dosing nopox tho. What did you use to dose potassium nitrate? everybody said spectracide stump remover was the easiest to do so I went with that.

Hi!
We can't get stump remover in Ontario Canada....it's on the "banned" list. I happened to have a pound or so of prilled KNO3 left over from when I used to build pyrotechnics.
I used to buy my potassium nitrate from a hydroponics store, it was the cheapest around (cheaper than the pyrotechnic suppliers). For Ontario Canada residents, I don't know if you can still get it from hydroponic stores...what I have left will likely last me the rest of my lifetime

Lasse · May 31, 2016

In Sweden we can get NO3 it from the grocery store as saltpetre (KNO3) or Chile saltpetre (NaNO3). We use it as a preservative. Probably the same over there

Sincerely Lasse

revhtree · Jun 1, 2016

I've noticed my monti corals react badly to lower PO4. Anyone else?

mcarroll · Oct 23, 2016

Almost everything should react badly to zero PO4. I've never know @Randy Holmes-Farley to quote me, but I wonder if he'd say something similar?

Some algae go toxic in response to that PO4 starvation.

Bacteria will out-compete most everything else for the remaining PO4, so look for some unhappy tank residents if you try to maintain zero PO4.

It will take a while for the condition to settle in as the cycling phosphate in the system (not on the test kit) slowly dwindles toward zero....not something I'd wait around for.

Combined with zero nitrates and you can really put a whomping on your tank....so be careful if you pursure this course much further.

I'd back off and shoot for more balance.....up to .05 ppm PO4 should be acceptable....and >5 ppm NO3 should keep the nitrogen cycle cycling.

Hopefully you're feeding the tank well – at least by way of feeding the fish well.

Cory · Oct 23, 2016

Cool happy it worked! If it were me id stop dosing nitrate until you see po4 raise again. Im guessing youve got a sand bed?

Waterjockey · Oct 23, 2016

Thanks for the replies. That was about 6 months ago or so, when I believe my liverock was still leaching phosphates. I've been able to reduce my carbon and nitrate dosing significantly since then. I have settled in on a balance of around 5ppm nitrates (I just use api for nitrates so the resolution isn't great), and phosphates generally test between 0.0 and 0.1 ppm (I don't have the ulr checker). I do have about an inch to inch and a half argonite bed, and I do feed a little heavier than I probably should.
The only issue I found was one trachy was very unhappy, and it turned out it was the 9-9.5 dkh I was keeping at the time. I now maintain around 8.0 dkh and it's puffing up great now. I just hope it starts to grow back the tissue it lost

I was intrigued with seeing the "nutrient limiting" theory in practice and being able to tune my "testable" levels wherever I wanted with careful adjustments of carbon and nitrate inputs.

On a side note, this was after I had neglected my tank for sometime after 2 "crashes" (my fault) in a relatively short time period...my nitrates were unknown...off the charts..160+ and phosphates 1.0+. I got them where they are now with doing nothing else but dosing carbon, and then carbon + nitrate.

BoneXriffic · Oct 23, 2016

I wouldnt chase po4. Good husbandry, and not over feeding. The tank will balance it self, and run at a po4 level. Out side assistance is only neccesary in rare cases imo. Just an opinion though.

I dont blink twice seeing a .2 but typically i run at a .08

mcarroll · Oct 23, 2016

Yes @BoneXriffic , it's not a matter of chasing.

It's a matter of not (never) driving PO4 to zero. And knowing that levels up to around 0.05 ppm (double NSW levels) will be beneficial in many or most cases.

Zero PO4 can be OK in the short term because test kits don't pick up all phosphorus in the system, but if you're doing anything to export PO4, maintaining that condition will eventually be likely to cause problems. Not everything can compete equally well for limited resources of it, so you risk favoring critters you don't want.

Between toxic algae and coral problems, it's worth knowing about.

reeferfoxx · Oct 23, 2016

mcarroll said:
levels up to around 0.05 ppm (double NSW levels)

According to RHF, NSW PO4 is 0.005ppm. Therefore, 0.05ppm would be 10 times the amount of natural sea water. I personally, don't go above 0.02ppm.

mcarroll · Oct 23, 2016

Thought it was 0.025 ppm (my bad – that's OK but was just a comparison for perspective – not the subject of the post.

There's no "double the PO4 of seawater" strategy.

Also, 0.05 was not plucked from air. Jsut tired of digging up the same links over and over....but I guess that's my fault too.

Hang on....

reeferfoxx · Oct 23, 2016

mcarroll said:
Thought it was 0.025 ppm (my bad – that's OK but was just a comparison for perspective – not the subject of the post. There's no "double the PO4 of seawater" strategy.

Also, 0.05 was not plucked from air. Jsut tired of digging up the same links over and over....but I guess that's my fault too.

Hang on....

No worries. I make mistakes all the time.

mcarroll · Oct 23, 2016

[URL='https://reeformadness.wordpress.com/2016/10/13/high-phosphate-requirements/']High phosphate uptake requirements of the scleractinian coral Stylophora pistillata [/URL]is my favorite reference on this.

Just need to get used to these links being here.

BoneXriffic · Oct 23, 2016

Nsw will have different numbers depending on where they are tested.... .025 has been found as well as .0025...so neither is right or wrong it just depends on factors

reeferfoxx · Oct 23, 2016

BoneXriffic said:
Nsw will have different numbers depending on where they are tested.... .025 has been found as well as .0025...so neither is right or wrong it just depends on factors

Can you reference that to support your claim of 0.025ppm?

Randy Holmes-Farley · Oct 23, 2016

NSW levels do depend very strongly on location. Whole ocean averages are higher than surface waters by a large margin.

reeferfoxx · Oct 23, 2016

Randy Holmes-Farley said:
NSW levels do depend very strongly on location. Whole ocean averages are higher than surface waters by a large margin.

All the information I have found has shown po4 levels to vary from ocean to ocean. The margin between each location tested does not vary greatly? In fact this chart shows it don't go above 0.0033ppm

http://www.seafriends.org.nz/oceano/seawater.htm

Randy Holmes-Farley · Oct 23, 2016

reeferfoxx said:
All the information I have found has shown po4 levels to vary from ocean to ocean. The margin between each location tested does not vary greatly? In fact this chart shows it don't go above 0.0033ppm

http://www.seafriends.org.nz/oceano/seawater.htm

You need to convert those units if you want them in ppm phosphate. ug Atom/L is the same as micromoles per L. So you multiply by the molecular weight of phosphate to get 3 ug-atom/L phosphate = 3 micromolar = 290 ug/L or 0.3 mg/L

Randy Holmes-Farley · Oct 23, 2016

Check out Figure 2A on this page. It shows the depth profile as you link does, but in uM.

http://www.whoi.edu/page.do?pid=131276

Both graphs clearly show surface seawater has far less phosphate than the deep ocean, so people quoting whole ocean averages get a very different answer than surface water values.