I had to use RW cubes to buffer them on both sides or it would just wash away. Made a load of holes in it with a screwdriver so the water flows freely. Im trying to come up with some kind of mesh that i can glue to the pipes and do away with the rw altogether.
I think the PH is sorted out now though, I fed with PH 5.2 this morning and the run off was 5.7

I was reading about Advanced Hydroponics Micro. They say it has ph buffers in the solution to help with micronutrient uptake. Looks like i made a good choice:clap: