[APD] Re: Aquatic-Plants Digest, Vol 14, Issue 38

[Thomas Barr <tcbiii at earthlink_net>]

>Personally, I haven't yet had the guts to add phosphate to my tanks
>except in clay ball form.

Why, ya chicken? 

>I typically use soil with peat as a substrate
>and amend it with clay fertilizer balls. I'm sure there is a substantial
>amount of P getting into my water via leakage from plants, fish, fish
>food and decaying poop from snails and fish.

Relative to N, this is not the case, the fish food is very heavy in N:P ratio. 
PO4 limitation is not that bad in plants though, still, it will cause them do better and grow faster if you add it and it clearly does not encourage algae.
I'd have more algae than anyone if that where true.

 I should like to know more
>about phosphorus/phosphate uptake since Tom has talked about algae being
>able to utilize organic phosphate complexes that macrophytes don't use.
>Suffice to say that algae conditions in the aquarium generally benefit
>from frequent water changes to reduce organic phosphate and other
>"pollutants".

I think water changes simply allows you to have more managable levels of nutrients w/o testing so much.
I do not think the DOP is causing algae blooms, but algae do have that advantage once they do bloom.

>Thinking of what Tom has said about macrophytes preferring mineralized
>phosphate, I'm wondering if it wouldn't be good to supply this using
>clay balls in lesser amounts but more frequently. This tends to keep a
>higher concentration inside the clay ball for preferential root uptake.

Simply because the plant takes up PO4 through the roots in nature does not mean it prefers anything.
You can see the growth differences in a nutrient rich tank vs the substrate.
You can put all the PO4 in there you want and not get the same growth/plant production vs the water column.
Several studies show that even cutting the roots off, did not change the rapid growth they saw when the water column was non limiting. So if the substrate was that critical, why no change in growth after removing the roots?

Why do we not see a slow down in growth after a pruning and root removal?

>I'm not convinced at all that increasing nitrate & phosphate in the
>water do not cause algae to grow faster. In other words, I believe that
>if you increase them in the water you will stimulate algae growth.

Okay dokey, where is my algae then?
You say it does, yet my tanks are mighty clean.
I've had high PO4 for 10 years at least.
I have no idea how many add PO4 to their tanks these days but it's a rather large number.

I have tanks with no herbivores,rich nutrients, light, CO2, algae free. Stable and easy to maintain too except for all the noxious weed growth.

>Of
>course, when the macrophytes are growing well, they sprout new leaves
>and may keep ahead of epiphytic algae and also shade out algae at lower
>levels. New leaves also lets you prune out the old algae covered leaves.
>We humans, and our algae eating pets, are agents in the competition
>game.
>Steve

True but non CO2 tanks have the same observation, where's the algae?
Less light, CO2 limited algae. 
The rate of growth is slower for both the algae the plants.

But plant needs/demands are still being met. 
So no algae.

Regards, 
Tom Barr




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