hydro question "pump size"

i tried the bigger fill house and still it does not fill properly. Should i get a bigger pump? im using a 400gph pump for a 4x4 tray, and a 40g res. and whats a good feeding schedule for them also how would i prevent root burn when they start comin out the bottom of my pots. there sittin there 30m at a time with out water. please clarify this because im gettin frustrated pretty quick. soil wasnt no where near this complicated..lol. thanks in advance..

and how high up my pots does the water lvl need to get to before shutting off, right now its about half way up.

How long is the hose from the pump to the tray? I used a 564gph pump of a 4x2 tray and it worked way to good I even had to put another drain in it. Are you sure the pump you are using isnt clogged or the tubing isnt clogged in anyway or a bend in the line somewhere that could restrict water flow. Check for all these things before wasting your money. When u say root burn do you mean the roots are exposed to the light so they burn? If google hydroton I believe its called or go on HTGsupply.com and look under grow medium I believe its on there. Thats what I used they work alright but it leaves a dirty look in your water no matter how many times you rinse them off only downfall.