Well, many plants don't really need circulation, I have no idea with aquaponics whether circulation is important and what do you mean by dunking pool? For humans?

When you turn off the water to the filter it will kill the beneficial algae but w/out fish that may be okay.

@ PKponder the dunking pool is occasionally for humans.

I agree. Filtration quickly becomes stagnation when the water flow stops. I would filter 24-7 to prevent any bad bacteria from getting a chance to get out of hand. And I would test the water on a regular basis as humans tend to introduce their own bacteria. Remember you are dealing with a closed system.

Its the leeches that freak me out. They have gotten on my hands when working in the pond before--no pain...just gross.

Leeches? In your pond?

I'd clean the pond of those things.

They are a natural part if you have fish. You can put a bit of liver in the pond and pull it out when the leeches are feeding on it to get rid of some of them but there are always more.

I have to say we've never had leeches in our pond so while I'm sure it's "natural" I'm not sure it's the norm.

They aren't very big like the leeches they use to use to medically. They are tiny and the ones I have seen were a flesh color. I haven't seen any lately but I have started over with my pond about 5 years ago so maybe I've been lucky and not imported any from plants or visiting birds. You can read about them here- http://www.pond-life.me.uk/fishhealth/piscicolageometra

They are very common. Thank goodness you haven't' had to deal with them.