My post here will not be all that different from the replies that have
already been given on the Aquatic Plants Digest. The ppm scale really is
a weight based scale, it was used very early in chemistry but is now
rather unfashionable. Most things are now given the more meaningful units
of molarity eg 1ppm Fe = 18x10-6 Molar or 18 micromolar.
Alan, a little technicality can go a long long way, you just never know
when you may be able to advance things along by experimentation. Ron
finding that shell grit is useful was probably pure experimentation on
his part and yet it is useful for some species. Certainly the growing of
aquatic plants has been made easier by the careful attention to detail of
a few who were not happy with how things were done and so they advanced
things along (and also made themselves a good deal of money into the
bargain).
Thinking of this sort of thing, Adrian would you know if anybody has
published information on the growth rates of fry with increasing nutrient
concentration (Preferably with identical water quality perameters ie just
adding Nitrate)? It is probably a very important question for aquaculture
and may well be of interest in our discussions here. It is easy to think
that empiracly it must reduce, but is it something in the water that is
merely correlated with poor water quality.
Has anybody reported the production of growth retarding substances by
rainbow fry. I do not know what the animal term for this is, in plants it
is called allelopathy. I know that it has for Discus and Koi, but have not
heard anything from rainbowfish.
Having asked all this, I will throw my hat in the ring with Andrew Boyd.
The thought of having a sardine can of a tank with no plants does not
sound like a real tank to me. One of the funniest sights I have seen in a
long time is my male nigrans and praecox fighting. They spin round in
circles trying to get to one another and because they are so evenly
matched they cannot. They break off to take a couple of gills full of
water and then swing back in while they think that the other is off
guard. This would not happen in a tank without space.
Peter Hughes