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Jeff's ("Kudzu") substrate query

Jeff's ("Kudzu") substrate query

> Now I need a substrate under the gravel that won't leak out and cloud the
> water with the current.

Two possible alternatives would be either Terralit, made by Aqualine Buschke
or Flourite, made by Seachem. Both are granular materials and should not
cloud your water if disturbed.

> Next question. Will a proper PMDD mix provide plants with all the
> nutrients
> they need (in plain gravel) or do they need something from the substrate
> that the PMDD can't supply? If so I might be better off to go this way.

Now THAT is a question. I have gathered all of the ingredients for PMDD and
am looking forward to trying it in a tank. I would HOPE that it would
provide complete nutrition for the plants - I mean the theory behind PMDD is
that you can vary the formula based on your observed results. One of the
most important purposes for the substrate (aside from anchoring the plants)
is to provide bonding sites for nutrient ions. Plain gravel won't have much
affinity for attracting and holding nutrients in a form which is available
to plant roots - I believe this is one of the reasons why it is usually
recommended that delicate species not be put into a newly setup tank for
three months. During that time, mulm would have a chance to build up in the
gravel bed and mulm has a much higher CEC than plain clean gravel so there
are more bonding sites for nutrients and thus more nutrients available for
the plant roots.

Now whether the source of those nutrient ions HAS to also be in the
substrate or could be in the water column (and would migrate into the
substrate) is another question.

If you used Terralit in the lower strata of your substrate, it HAS
fertilizer incorporated into it plus it apparently (according to the box
anyway) has the ability to bond nutrients so that it should be able to
accept some of the nutrients in PMDD and make them available to the plant
roots. I don't know if Flourite has any fertilizer component or if it acts
solely as a bonding site for nutrients.

There ARE certain nutrients which some plants prefer to absorb through their
root systems as opposed to through their leaves but that really depends upon
the plants you want to grow. In the type of tank you are talking about (a 20
Gallon Long tank for native Darters) I would suggest that you take a good
look at the conditions in the streams where you collect the fish and base
your plant choices on that. Probably some Vallisneria, Didiplis diandra
(Water Purslane), Ludwigia and Fontinalis are plants which come to mind as
possibilities. If you are doing a native tank, why not use native plants?
There should be some plants in the same brooks where you collect the Darters

James Purchase
Toronto, Ontario