Hey guys, i'm starting 2 18gal tubs with a 5" net pots 2 each in a tub. If I put like plexi glass to divde the roots would it work ? also how frequent i would need to change the res water ?
There's no need to keep the roots separate unless you plan on splitting up the plants later on. How often you change the water depends on a million things. If you have to adjust the pH a lot you'll change it every time the ppm's get too high. Supposedly if you run Lucas formula and RO water, you can go up to three full harvests without flushing!
I agree with waitwtf however would strongly recommend haivng a recirculating system if you have the space, this will save you alot of time when it comes to adjusting and dumping nutes.
Use CFL's for extra lighting i wouldnt grow in 18gallon tubs though, reservoir changes would be a bitch and you NEED to change that water. I dont see how you could go three harvests without changing MAYBE 3 weeks with that 18 gallon res. also if youre using those tupperware storage tubs, make sure its black; any other color will let enough light in to mess with your roots. just follow rumpleforeskin's bubble bucket how to; prob your best option if you have no idea where to start.
How long are you planing to veg your plants and how big are you trying to get? If you looking to veg for a month and flower for 2 month then I think there is no need for such big container(waste of nutrients), roots will not fill up the entire space. 5 Gal buckets will allow plants to get to a good size . I have seen pictures of 6ft tall plants in 5gal buckets... With such big container you must have a powerful than average air pumps and good air diffusers, to avoid root rot and other crap due to poor oxygenation Goodluck with your project.