Backyard Aquaponics
A place to discuss aquaponics

There is enough I don't know about your system that I can't answer those questions. I might not be able to answer some of them even if I did know everything I needed to but I'll try to get you started where you can find what you need.

For the aeration in the biofilter to get the media boiling (it should look like a light boil unless you're trying to clean the media) - This is going to vary with the amount of media, type of media and shape of your container - Here are some pump recommendations based on media volume (the numbers in the pump name are the max LPM the pump delivers (at least in this case)) - http://www.evolutionaqua.com/acatalog/K1_Filter_Media.html. I think their estimates of the pump needed might be too high but can't be certain.

Take a look at this and see if it answers your questions on aeration in the DWC troughs - http://teca.fao.org/read/8397

Tilapia are very durable fish and can tolerate very low dissolved oxygen levels. On the other hand, they'll grow better with good conditions so if you're planning on lots of fish then you need to aerate (keep the DIO above 5 and preferably higher). If your stocking rates are low just water movement may be enough. Given what you've told me I would aerate the fish tank especially if you see the fish hanging out up at the top of the tank like they need air. If you want to figure this more accurately then this article by Dr Rakocy should help - https://thefishsite.com/articles/tank-culture-of-tilapia.

Hope this helps

Oops, forgot about the fish switch. I think the DO requirements for Catla Carp will be similar to Tilapia. Their transport requirements from this abstract (https://www.researchgate.net/publication/267559592_Oxygen_consumption_of_carps_during_live_transportation) look like they are in the middle of the Tilapia range from the Rakocy paper and carp are usually pretty good at survival in low oxygen water.

Probably a good idea. A lot of people will quarantine the fish in a separate tank so that they don't introduce diseases into their main system.

6500°K - 7000°K is daylight and being old school that is what I would have used, with a little bit of heat output, but now they use COB LED, with red light added to the daylight.

COB (Chips on Board) , is a new technology of LED packaging for LED light engine. Multi LED chips are packaged together as one lighting module. When it light up, it looks like a lighting panel..


http://uponics.com/cob-led-grow-lights/
https://420expertadviser.com/grow-lights/cob-led/

The diagrams are a guide to output and height.