Hal wrote:
On Tue, 3 Apr 2007 17:05:18 CST, Altum
wrote:

I run my tiny pond much like an aquarium. I fertilize the water with
the same mix of bulk potassium nitrate, potassium phosphate, potassium
sulfate, and hydroponic trace element/iron fertilizer that I use in the
indoor tanks. Phosphate in the water column makes the WH and canna
lilies bloom like crazy. I don't see why it wouldn't do the same for a
bare-root lily.

That's interesting.

Yeah. I'm really into planted aquaria and someone here advised me to
treat my little pond/water garden the same way. Imagine my surprise the
first time I added my aquarium fertilizer with the phosphate and every
single WH bloomed!

It does sound suspiciously like it might contain the same stuff as a
numbered soluble fertilizer like 15-30-15, that I find at Walmart. I
don't know where these chemicals come from, or if they are in
combination with potassium but my understanding is they are simply
nitrates, phosphates and potassium.

The stuff at Walmart generally contains ammonium nitrate. The first
number in the N-P-K fertilizer ratio isn't nitrate, but nitrogen.
Ammonium nitrate is the most common source of it for fertilizer. You
can get away with burying a fertilizer spike with some ammonium nitrate
deep in a pot, but of course you wouldn't want to add ammonium to a pond
with fish. If you find a brand without any ammonium, I'm all ears!

What is the difference in using a mix of bulk potassium nitrate,
potassium phosphate, potassium sulfate? Sounds like potassium comes
with everything and I wonder why, and if it works better?

I use the bulk chemicals because 1) they're wonderfully cheap and 2) I
can tailor the mix to my individual tanks and pond depending on my water
change schedule and fish load.

The nitrate and phosphate have the potassium counterion (K, potash)
because aquatic and pond plants need a lot of it. Potassium is the K in
the N-P-K number. The chemicals are set up avoid adding undesirable
sodium and chloride to the water. Some people don't even need potassium
sulfate when they use potassium nitrate and potassium phosphate. I find
my plants do better with some extra potash so I add the potassium sulfate.

BTW, people in sof****er areas also add calcium and magnesium to the
fertilizer. My water is hard so I don't worry about it. I doubt it's
too much of a problem in most ponds since everyone tends to add coral
and/or oyster shells to harden the water a little for koi and goldies
anyway.

I saw mention of algae blooms with water column fertilizers. My 3
half-barrel pond has a LOT of plants and very few fish compared to a
typical formal koi pond - it's practically a veggie filter. LOL! If I
don't fertilize the water, the WH goes reddish, chlorotic, and straggly
and the algae grows like crazy. When I fertilize well, the WH gets lush
and green, the cannas bloom, and algae is much less troublesome.

I would expect a lot more algae bloom problems in systems with more fish
and fewer plants, since there are often traces of ammonia in the water
until it passes through the filter. Ammonia + iron + sunlight = instant
algae.

--Altum

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