For the love of god I hope you read this before you go to the depot and buy a bunch of shit you dont need. Dude people for some reason go WAY overboard on CFL grows. Im sure it is because so many people say you cant get good yields with CFL's or that you need like 100 watts per plant ext...THIS IS COMPLETE BULL SHIT!!!! I am so fucking sick of hearing this shit. The most simple, cheap, and effecient CFL setup you can possible make is with two 30 gallon rubbermaids flipped on eachother like you got there with those 20 gallons. DITCH THOSE 20 gallons. Buy 2 30 gallons at wally world. they're 10 $ each. You have a great fan, although for future reference and other people reading this all you need is a 4" pc fan with full power (usually 12 volts) All you need for lighting is 4 42 watt 3000k warm white CFL's for a total of 168 watts and 10,400 lumins. 5-6 plants will fit COMFORTABLE in 2 gallon grow bags. Since you have a can filter 4 would grow fine. For lights you buy a 4 light vanity fixture from walmart or the Depot. Its the cheap simple bathroom 4 light fixture. Take metal off and cut holes for sockets and put em through and seal with silicone sealent. put 4-6 passive intakes 2" in diameter. The purpose of putting your lights like this is the plants grow inbetween them so 100% of the light is being utilized. 360 degrees. The mian reason alot of CFL grows are shitty is because they put there lights vertical above there plants. CFL's HAVE SHITTY PENETRATION. Im sure you read this and know this but I just wanna say it. So when people do this they are only using about 25% of the light and most of this is just on the top 2-4 inches of plant. When you have your bulbs vertical and your plants growing aroundt hem you get 10+" of dense bud growth. I promise you if you are even just a half ass grower you will pull ATLEAST 2-3 OUNCES from this. I and my friend pull quater pounds from this. You should to. You have to be doing something seriously wrong to pull less. If you have a stringy sativa you will pull around 3 ounces with optimom growing conditions. A good indica or indica/sativa cross and you can pull a QP without much difficulty. You seem to have some good ferts so that should be fine. All together this setup cost 4 42 watt cfls=9$ each @ wally world=27$, 2 30 gallon rubbermaids @ $9 each=$18, 4 sock vanity fixture=$20, plus exaust fan, small table or pc fan to blow on plants to strenthen stems and nutes. You already have the last 3 things. So thats $65 for you and someone else a pc fan is about $4-5 for a good one. My box cost me $80 total to make. Also people freak out about burning leaves with CFL's. IF YOUR NOT BURNING LEAVES THE PLANT IS NOT CLOSE ENOUGH. If you burn a leaf just cut the burnt part off. I have yet to have a hermie in any grow I or my friend have done (knocks on wood) When your plant grows up around the lights just pinch the fan leaves down. Pinch the stem down and bend it towrds main stalk. If it snaps thats fine. Again no hermies from this. It will repair its self but it will stay bent like that way from light. Also a very importan thing to do is rotate your plants 1/4 turn every day. THIS IS VERY IMPORTANT FOR EVEN BUDS. If you do this right not only will you have 3-4 ounces of bud but that bud will be ROCK HARD NUGS. Just make sure the temps are 70-75 ideally. 75-80 is OK but any higher and .your gonna g.et airy buds. You have a nice fan so airflow will not be a problem. 168 watts= 3-4 ounces I PROMISE. If you want visual confirmation check out my Purple Chitral X Uzbeki log
https://www.rollitup.org/cfl-growing/167502-5-purple-chitral-x-uzbeki.html
Im 12 days into flower in that log. I did not create this box design. A guy named Lifeless did and he is a fucking guru for doing so. Believe me I overthinked shit before I did this to. Im so glad I decided to try this box because it is 1000% amazing. If your confused about the box design just post it and ill check tomorow morning after I get back from the gym. Dont worry, if you do it right you will be very suprised at how well CFL's will do. You can easily have a few of these boxes going and have a perpetual harvest as good as any HPS SOG. Just veg till about 10-12" depending on strain. If sativa flower around 6-8" and pure indys flower around 12"
Pce bro and good luck.