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Re: P & Fe

> I learnt that in land planting fertilizer, the 'P' element in N-P-K is to
> encourage flowering.
>But in Aquatic planting, conventional wisdom said that
> 'P' is supposed to be limited intentionally so to discourage algae growth.

That's one approach. What happens if you limit that element? Do you think it
helps or stops the plants from growing as well? Don't they need this as
well? You can do it for awhile but be careful not to run at zero. It's a
balance- not elimination. I had lots of P in my tanks for many years yet no
algae. I have no P now and I have more problems with algae. I add P and
algae problems go away. Conventional or not-P by itself does not cause
algae. An imbalance does. P doesn't grow algae, it takes N and others to do
grow any plant and algae. It's about a balance of nutrients(don't forget CO2
as a nutrient as well) with the amount of lighting. There's likely more than
these two that can be used for algae control. Each has a trade off.

> What if we limit the 'Fe' for algae control instead (as recommended in Diana
> Walstads' book) and then dose in more 'P'.

Same as above. 
Both methods work for limiting algae growth quite well. I've done both. Fe
did a better job at limiting algae actually. P is added from other sources
like tap water & food. Fe not so much, so it tends to be a more controllable
nutrient than P. But you can have laterite/flourite/iron tabs in the soil
since the plants have ROOTS and the algae don't. Also plants will fine with
no Fe in the water for up to about three weeks. No so with the algae. They
can't hang that long. Potted plants will be a good idea if you specifically
want to flower one plant and you could enrich the gravel while packing it
down well so to keep the P in there and out of the water column. If later
sometime in the future, you disturbed the gravel bed and there's some P
leftover you could have big problems. Pond places have tabs for such things.
Jobes sticks will do it too. You may not like the increased growth rate
though:) They can get quite big afterwards.

>Would it actually induce
> flowering (say, in the case for red tiger lotus) ?
> Anyone try this before ?

P additions are interesting in there effect and dramatic. Pulsing seems to
be what a few folks have decided to do when using it. I had much higher
amounts of P in my tap than what I now dose. I will likely add more to match
my old levels which were quite high. But I'm taking it slowly rather than
the big weekly dose that I use to do. Caution should be used and a test kit
when playing with P. Iron is much more forgiving IMO to the
plants/overdosing. Lower N levels(but not absent!) will help when playing
with these. 
Tom Barr