Thanks once again - ahh that answers the gravity question! It's a great system you have there. I was thinking a simple one way flow (swing check valve) http://imagehost.vendio.com/bin/imag...ve_1_union.jpg value might have done it with out the 2nd pump - or if the reservoir was below the buckets then by natural gravity.

What have you found with your experiment so far as when leaving water in the buckets at different levels?

I was thinking you could almost have a aero-bubble hybrid system - perhaps that would be a waste of time though.

Also does it matter if the reservoir is covered, does light effect the nutes when light hits them in any way? I remember hearing fluorescent light for example can effect oil in a deep fryer some way.

Anyway I am coming along nicely (thanks to you) and nearly completed my own "daddy-o system" :thumbsup:

I'll keep you posted! Thanks again for all your help mate - you rock!

(and I'll probably bother you again with a silly question - as after re-reading my last question, I barely understood it myself - clear as day as you say!)