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Re. Re. Phosphate limited tank??

>> My tank is 87 gal, 2x 175W MH lights, fertilize with PMDD, KH 8, GH 4,
>> PH 6.8, NO3 10ppm , PO4 0, Fe .1, and DIY CO2 injection.

>With a KH of 8 and pH of 6.8, your CO2 is 35+ mg/l.  That's pretty
>remarkable for DIY CO2, but do you really want it that high?

Hehe.. didn't plan it on getting that high.  I injected CO2 into my canister
filter but had a problem with the CO2 hitting the impeller and stopping the
suction once it had been running for a while. Concentrations were not that
great. Now I use an airstone directly below the intake so that now tiny
bubble are produced and sucked in.  The effect of this seems to be that ALL
the CO2 gets dissolved and my concentration shot up. Next batch I make will
have less yeast as I need less.

>> My problem is that the N increases over time.

>I'm not a PMDD guy, but it seems to me like the most direct solution would
>be to decrease the potassium nitrate content of your PMDD mix.

I use Potassium Sulphate only.  I'm not adding any Nitrates at all.

>> - - Starting to use TMG fert.  Thinking maybe I'm missing some micro
>> nutrients although I had hoped they would be in the tap water (no growth
>> increase when doing a water change)

>The PMDD should provide all of you micro nutrients.

It does?  Guess when it says chelated trace element mix it's iron and the
other elements to.

>> - - Using Jobe's sticks in the substrate. Question! The Jobe stick
>> recommended is LOW in Phosphates... since this is where I think the prob
>> is wouldn't I want low N and high P??
>> Already have enough N in the water.

>Jobe's sticks work best for supplementing specific, heavy-feeding plants.
>They aren't a great solution for nutrient shortages or imbalances that
>effect the whole tank.  You can get Jobe's sticks with different N-P-K
>values - you can get high-P formulas if you want.

>> - - Adding Phosphates directly to the water  while making some sort of
>> live sacrifice to the fish tank god not to bury me in a tankwide coating
>> of green furry stuff.

>Hagen's "PlantGro" fertilizer (someone in marketing there at Hagen leans
>real heavily toward incipid names for their products) contains a small
>amount of phosphorus; according the a letter they sent me a while back,
>the guaranteed analysis is 0.3-0.08-0.8.  You could add a dose of that
>stuff, and if phosphorus is the problem this should give your plants a
>kick in the butt.

But I'm also adding nitrate which I already have. Hmm does anyone know the
ratio between
N and P that plants use. IE for every 1ppm of P a plant will use up 10ppm of
N while growing??

>You might also try a *small* dose of a phosphate-based pH buffer.  For
>instance, Greg Morin told us some time back that SeaChem's phosphate
>buffers used as directed gave 80-100 ppm of phosphate; to dose your
>tank with 0.1 ppm phosphate you would use 1/1000th of the directed dose.

You gotta be kidding me!?  That thing must be just a jar of phosphate.
Guess you add just one or two grains.

>More generally, adding phosphate in any form is at best an indirect
>solution for a high nitrate problem, and may not solve your problem at

Thanks for the info

|Roger Miller