Anyone considered adding co2 tablets to their water supply? It supposed to work check these out.

New! 100 Co2 Tablets: Basement Lighting Hydroponics and Plant Grow Lights

Co2 can be absorbed through the roots just as efficiently as the leaves. Check this:

CO2 Root Absorption

These slow release oxygen tablets may be of interest also, 25 for £1.10

Fish and Fins, UK - Goldfish online supplies

Hope this is of interest, let me know if it is. CHeers.