Graham Broadbridge wrote:

Most tanks are not short of nitrate. Tanks that are short of nitrate
normally have lots of light ( more than 2-3 watts per gallon of flourescent
light) and injected CO2 at around 15-30 ppm CO2, and lots of fertilizers.

Graham, your statement is generally true of tanks with fish, but because Shawn
has the green water, he is more likely in the low-nitrate category than in the
"most tanks" category you describe.

Green water is unliely to be solved by addition of KNO3.

Experience argues against this statement. Many cases of green water have been
solved by increasing NO3. The cure is not quick, however, and there must be a
substantial mass of healthy plants in the tank. If the green water has lasted
too long, the plants may not be able to recover fast enough to prevent another
greenwater explosion. The best route in this case is:

* 50% water change, dose Nitrate to 5-10 ppm (I believe Shawn is low)
* Three day blackout
* 50% water change, dose all ferts.


Best bet is to
use UV sterilization of the water column to kill the algae spores.

On this point we agree, if by "best" you mean the easiest and most foolproof.
But also the most costly.