Jacky,

>....rainbow trout can be fed with fresh earthworms or other types
>of worms. May I suggest that you consider growing worms using
>the filtered solid organic material from the fish tanks.
>Plant wastes can also be added to the earthworm culture."

Actually, we have quite a bit of experience with vermiculture (cultivation
of worms) and the system we are working on focuses on the
full biodiversity of the soil ecosystem, rather than epigeic worms (surface
feeders) or microbes (composting). There are the nightcrawlers (anecic
earthworms) which play a big role in soil formation as well as micro and
mesofauna that are important in the decomposition process and nutrient
dynamics. In ecology, they use the term "ecosystem services" to describe
the role of nature, for example, to purify a stream that has been polluted.
So we are working on a system to employ that free labor a little better
than our current systems.

Q: how much of this organic waste matter can you get per day ?

A general rule of thumb to predict the amount of solids that will be
generated from production of fish is 0.3 x kg feed fed (this will vary
with the type of feed). So for every 10 kg of feed fed, you will produce
3 kg of solids and at 5% N, would have 150g N. So in our system
described in the paper we have 27,240kg feed fed/y x 0.3 = 8,172 kg
solids/y or about 22kg/d.

Paul R. Adler, Ph.D.
USDA-ARS
45 Wiltshire Road, Kearneysville, WV 25430 USA
Web site http://afrsweb.usda.gov
voice  304.725.3451 x352     fax    304.728.2340