We bought a barrel that looks kinda like this:
The downspout doesn't actually go INTO the barrel;
since the barrel lid has a 1' recess in the top,
we just drilled holes in it and positioned the
downspout over it.
We bought a roll of fiberglass "window screen" cloth,
cut an 18' square, and wrapped it over the top of the lid,
holding it in place with a ring of copper wire
twisted tight into the gap under the lid.
It ain't neat and pretty, but it was quick and cheap
and it will keep the mosquitos out.
And we put the foot from a pair of Sweetie's old pantyhose
over the bottom of the downspout to filter out anything that
washes down from the gutter- I think it worked pretty well, since
it's full of dead leaves & random sediment this morning.
Glad to hear you seeds are doing so well;
I've had some minor success in that area myself.
Cleaning up last month, I came across some tomato seeds
that my mom had sent me three years ago, from one of her
"Brandywine" plants that had been especially productive & tasty.
I assumed they were long gone, but went ahead and planted them
in an egg carton in my kitchen window for "just in case"...
and wouldn't you know it, they've all sprouted!
Mom said it was a MONSTER tomato bush in her yard up in PA;
I can't wait to see how they do down here in NC!