Backyard Aquaponics
A place to discuss aquaponics

I dont think the sump really does anything. I guess it adds a bit more water to the system, but you might be better off just using the fish tank to drop your water back into as they do in BYAP retail systems.

If you cut the duckweed barrel lengthways you would be able to grow a lot more duckweed.

Also if I understand what you are doing correctly, I think the water level of the duckweed tank will be lower than the fish tank. Are they connected? if so you dont want the fish tank to be able to siphon back into the sump during a power outage. But I might not understand.

You want the path of your solids to go from the fishtank into the grow bed where worms can do their thing. Then nice clean water dumps back into a sump or directly back to the fishtank.

Sorry if I've misunderstood your plans.

Can you just list the path the water takes. eg...

fistank
grow bed
sump top
sump bottom
fish tank

Or whatever it is in your case.

And I think your duckweed tank wont see enough light, unless you plan to add lights under your growbed.

whats the 'small biofilter' - the GB can be the biofilter. +1 on bullwinkle's comments too. and what is holding up the corner of the IBC GB above the blue barrel?