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Re: substrate fertilizers and others

G. Kadar wrote:

> I have done the experiment in regards to whether the nitrates or phosphates
> leach out of the substrate when high dose fertilizers are used.  There was
> no leaching whatsoever.
> As to using other fertilizers, I think it depends on what kinds of plants
> are in the aquarium.  Some plants can 'leaf feeders' or are floaters that
> depend on the water column for their nutrients.  Then there are the 'root
> feeders' like crypts, vals, sags, and swords.

I recently advised Craig David that he might want to vaccuum his substrate
to help remove fertilizers added directly to the gravel.  I'd like to
clarify that the reason for doing this is *not* entirely the belief that
fertilizer might leach from the substrate.

There is a constant supply of nutrients to most aquariums through fish
feeding and the resulting wastes.  A practical way to keep those nutrients
under control is to make the plants use the nutrients.  If the plants are
provided with a rich supply of nutrients in the substrate then there is
considerably less reason for the plants to compete for nutrients in the
water.  If the plants don't use it, then the algae will.

I believe in supplementing plants through the substrate as much as
possible and I thought that Ms. Kadar's results were very encouraging. But
I think it's probably a bad idea to add major nutrient supplements (N and
P in particular) to the substrate if there is already an excess supply of
those nutrients in the water.  It's important that your tank must need the
additional fertilizer before you add it to the substrate or you may simply
be indirectly feeding the algae.

> Everyone has to determine which balance of nutrient provision works best for
> their particular situation.  Fish loads and CO2 injection or lack therof
> also come into play.   I don't think anyone can generalize, only provide
> information on their own experiences.

I think that generalizations can be made.  Some methods do produce good,
reproduceable results (Mr. Subliminal mutters "Dupla") and they are
evidence that generalizations can work.  But in the context of giving good
aquarium advice it would be tough to make a generalization that applies
every time.

That said, I have to admit that "Don't add more fertilizer than your
plants need" seems to me like a pretty good general recommendation.

Roger Miller
opining yet again.