Harry wrote:

Will using Clorox or hydrogen peroxide not damage pose a danger in the
summer when watering delicate seedlings in the greenhouse? Obviously
I would rinse the inside of the butt well, but if there are traces
remaining?


The chlorine from the Clorox will evaporate in a fairly short time. The
best way to ensure this is to leave the container empty after rinsing it
and open so that air can circulate in it. Give it a week and it will be
long gone.

Hydrogen peroxide will not damage seedlings if the concentration is less
than 0.1%, a level easily attained after a single rinse. In fact, the
peroxide is commonly used as a disinfectant in greenhouses and is used
on farms as a fungicide spray (at the 0.1% level). The company that
manufactures the hydrogen peroxide as a fungicide has a demonstration
that features a bowl of goldfish swimming in a 0.1% peroxide solution.

On the other hand, the stuff they sell is a 27% solution and you DON'T
want to get that on your hands. However, if you stick with the grocery
store stuff (about 3% strength), people use it as mouthwash (I usually
dilute it at least 1:1).

If you're using the container as a collector of rainwater to water your
seedlings, the best thing to do is to keep out any light. Without light,
the algae won't grow. This means at least a cover on the container, and
if the container is plastic, probably a couple of coats of paint to keep
light from filtering through. You could even build a box around the
container (with some provision for getting the water in and out.)