Cultivating Elodea

> From: Thomas Catrambone <tcatramb at ix_netcom.com>
>     I am a science teacher and periodically we use elodea in experiments.
> We normally buy it at a local pet store, but at times it's not available
> and when I need to do a lab it can present a problem. Can you tell me
> how to root it, and what elements and concentrations I need in a 10 
> gallon fish tank. Other information like temperature and what else I need 
> to know would be very helpful to my students and I. I have a greenhouse 
> to grow it in.

Elodea will send down roots on its own so you can just float it
in a tank. I'd put a layer of ordinary black garden soil in the
bottom of your tank and cover this with a layer of clean sand.
Don't use soil or sand you collect from near natural water bodies to
avoid introducing nasty types of algae. The soil will provide most
of the micro-nutrients you require for growth. It is a good idea to
include daphnia and snails in the tank especially if it's going to
get direct sunlight.

When you purchase your Elodea, inspect it carefully to make
sure no green hair or filament algae gets into your tank.

If you have very soft water, you could add 1 tsp of CaCO3/10 gal to 
your water to increase the calcium content. It would also be good to
add potassium and magnesium. You could use the following from the 
PMDD dosing method:

In 300 ml of distilled water dissolve 2 tsp K2SO4 (potassium sulfate)
and 3 tbsp MgSO4.7H2O (fully hydrated magnesium sulfate, aka epsom salts)
If you dissolve CO2 in the water, you might need about 1ml of this
per day or 5ml per week. If you're going to add nutrients like
this for which there are no simple concentration tests, you should
change about half of the water in the tank with cold tap water
every month.

The soil will provide some initial amounts of nitrogen and phosphates,
perhaps enough to create a green water algal bloom. That's what the
daphnia are for. To get faster growth, you can add an ammonium
fertilizer to get 1-5 ppm ammonia. You will need very little.
Ammonia test kits are cheap and readily available in aquarium and pet
stores.  I'm assuming there are NO FISH in your tank. If there are, 
the fish will supply all of the ammonium you need. Addition of more
could be harmful or lethal to the fish.

The plants will grow much faster if you have a CO2 source in the
tank. Organic soil (no more than 5% organic) will provide some
CO2 or you can use the yeast method to generate CO2. See krib
archives. If your pH is rising, your Elodea is using CO2 from
carbonate and you need to dissolve CO2 in the water (or add
more carbonate, and change more water).

The temperature for Elodea is not critical. It will grow in temps
from 60F to 80F for the species available in the aquarium trade.

Don't use any kind of filtration such as biological filtration
as for fish aquariums. This will cause the useful ammonia to be 
converted to nitrate with an accompanying reduction in pH. Plants
MUCH prefer ammonia as a nitrogen source.

Good luck! Elodea are excellent plants for growing with fish to
keep the water conditioned and oxygenated.

Steve Pushak      spush at hcsd_hac.com  Vancouver BC Canada