Okay, thanks. We have a waterfall and a good air bubbler. Hope that
is doing the job.

I'll be on the lookout (or smell-out) for hydrogen sulfide. I know,
that's hard to miss.

Joan

CO2 is not that much a problem: add extra aeration and it's done with. Or
plants will use it during the day (but make it during the night) - so air
stones or venturies or water falls or ANYthing that will increase
oxygenation is OK and will off gas the CO2. The gas you need to be worried
about is *hydrogen sulfide*: this will KILL your fish. - it's the stuff that
smells like rotten eggs when you disturb pockets of it, like when you clean
the pond. What's the save level for that? ZERO

Lee