How often should i flood a flood and drain table?

wanted some input on some hydro question? i have a 3x3 tray with a forty gallon resivor underneath. the light is 100o0 watts but there is cross over light tto so more like 1100 to 1200 watts on the tray i have it set p to flood for 15 minutes right when the lights kick on and 4 hours later for 5 min then four hours after that for 10minutes it never feeds while the light are on and the plants seem fine. whats a general rule of thumb on how long the tables should be flooded?

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What medium are you using. How old are plants ect...

Ok ill do you one better than garm.When i was growing ebb and flow i had a 2'x4' table with 6 plants.These plants set in net cups filled with pea gravel,These net cups sit in a lid that covered my flood table.The flood table has no other medium inside of it,just open air.Im not going to say it was perfect but i got a few grows out of it.If i might ask why are you changing intervals on how long the flood is.One thing i learned is mj likes routine.I would water mine when lights come on 5 min.then every 3 hours after that for 5 min.They would get 1 watering with lights off because the roots would dry out cause of no medium being in the flood tray just roots.If there is a medium filling your tray you wouldnt have to water as many times as i did cause the medium will help hold on to the water.So it is going to have to be a trial and error thing.this will take a whole 1 day light cycle.Start off feeding when the lights come on.do not feed again until you notice a slight droop in the leaves.DO NOT let them totally droop.It will not kill them but isnt good.Now this is going to be your base time in veg.what ever the time difference is subtract 1/2 hour so that you water well before they start to droop.
When you go into bloom you will start on the same schedule but as the plant goes further into bud,the plant will want more food which means more and slightly longer intervals.The 5 years i tried to master ebb and flow I never got an exact answer on this topic,but my hydro guy suggested this way to find out when that paticular plant wants water and it helped me get a better grasp on the situation.

Thanks for the info the plants are week 5 and they seem great. i haven also used ebb and flo for like 5 years now, i just recently learned about this web site so im asking everyone all these questions i have that have been left UN answered for years lol. But i know that mmj like routine but check it. when you flood for 15 right when they kick on they get a really good feeding. They probably don't need the second feeding im using ROCK WOOL but remember that when you are using a flood and drain table not only are you supplying the plants with water you are supplying them with oxygen as well. so hence that's why the second one is really just a quick little dip for them and then i always make sure to feed them about 3 hours before the lights kick off and never eve feed them why the lights are off i found that if you do this you can run into root rot especially if you aren't monitoring the temp of your water and you get a cold night. All in all i just really i guess wanted to see what every one else was doing. i will say the it is the most cost effective efficient method i have ever used and i have tried every which way and yield the most out of this dont ask me why the second in command was using hydro-ton buckets. but that was a pain in my ass. i notice that sativa strains for some reason dont drink as much as indica though.