Oxygen levels are great! no bad water at all!
The drip system is good at 2.1 gph.With the drip system going 24/7 and the water breaking the surface to make oxygen**** ( not good enough at your stocking levels) ***** I will have a 100% clean and oxygenized tank every day.
Co2 system is going good to.Aquatic plants are comming,and so are fish.Waiting game stinks!
As someone mentioned plants will need light, BTW what kind of plants are you planning to grow?
Adding CO2 with the stocking levels you plan may cause an algae bloom which will require more water turnover. You will also need supplemental air, the depth of the 55 gallon drum will require a powerful air pump and large air-stone, the air has to come from the bottom to keep the waste from layering on the bottom.
Can you post some pic's of your set up?
WOW! you are like the strongest critic I have yet to come across.
I'm not critical, actually I want you to succeed but I want you to be aware of the pitfalls of trying to raise catfish in a 55 gallon/48" tall barrel. As you surmised I raise/keep tropical fish (75-80 degree) and breeding in 10/15/20 gallon tanks is easier than 55gallon "upright" drums. Your challenge will be keeping the water fresh and clean. To grow quickly, fish need a lot of clean water, a lot!
Catfish are more tolerant than tropical fish but the amount of food they need can outstrip the amount of water a 55/48" tall 55 gallon drum is capable of providing unless you can add a "whole lot" of clean water.
Take the same 55 Gallons and spread it out over an area of (48in X 24 X 12)/231 ='s 60 gallons with the same water turn over and you have a much greater surface area capable of supporting the stocking levels you are proposing. Surface area is the key to exchangeing ammonia/nitrate/nitrite waste + adding air/oxygen to the water to increasing your success rate.
More later ... and looking forward to your success.