Which PMDD Recipe to Use

[st_stephen]

The fert faq is great and there is tons of info...

I just wonder what is the best PMDD Recipe?

This is from AquaBotanic:
2 Teaspoons (~14g) K2SO4 (potassium sulfate)
1 Teaspoon (~6g) KNO3 (potassium nitrate)
2.5 Tablespoons (~33g) MgSO4-7H2O (aka epsom salts; omit if present in trace element mix)
1 Tablespoon (~9g) Chelated Trace Element Mix
(7% Fe, 1.3% B, 2% Mn, 0.06% Mo, 0.4% Zn, 0.1% Cu, EDTA, DTPA)
300 ml (1.5 cups) distilled H2O

This is th "Conlin and Sears Latest PMDD formula" from The Krib:
1 tablespoon chelated trace mix
1 tablespoon MgSO4+7H2O
2 tablespoons K2SO4
1 tablespoon KNO3 (varies, depends on your nitrate)
Mix with 1/2 liter of water

Also, the faq talks about adding phosphates, but it's not in the pmdd recipes I've seen - Any advice on that?

Thanks!
Stephen

 

[phanmc]

The original PMDD method reasons that phosphate is the leading cause of algae and tries to control algae by limiting phosphates, which is why many PMDD formulas exclude it. Limiting phosphate will also limit plant growth so you will still need to include that in your fert routine.

I don't use the PMDD method anymore, having switched to Tom Barr's estimative index method, so I can't really say which formula is better. Judging by the amount of MgSO4 advised in Aquabotanic's recipe, I think I'd use that if you're using RO water or have low gH.

 

[djlen]

Gotta go along with phanmc on the points he makes. Opinions have changed over the years and the good old regimes out there aren't so good any more.

I don't like either one of them due to their being incomplete, IMO.
It's not a good idea to use the PMDD principle in any but low light tanks because individual tanks have individual needs which, in my tank's case are frequently changing an so the dosages need to be tweaked to accommodate those needs.
The better way to go would be to download Chuck's Desktop Calculator or the Fertilator and keep them handy, using them as a reference or starting point and then tweaking from there.
I have 40 gal. that has changed little in the 12 - 14 years of it's existence and I could probably devise a PMDD regime for it if I wasn't constantly experimenting with this or that.

Len