Backyard Aquaponics
A place to discuss aquaponics

I put some small lettuce seedlings that I started in rockwool into hydroton filled 3" netpots..
The seedlings were really small ~ 1" and they don't seem to be coping well a couple died and I replaced them and overall they're not looking well and haven't grown in the past 2 weeks..

What size seedlings do people generally put into NFT pots.. ???

FWIW, the NFT system I'm building is a 4" pipe with 3" netpots. Instead of setting up wicks for each pot, I'm going to raise the level of the water to be slightly above the bottom of each pot.

For NFT, definitely make sure to filter the water well before sending to the pipes/gutters or whatever. Even with well filtered water, I still get gunk in my nft pipes (well mine have deeper water in them than just a film but anyway.) If those gutters are open top and exposed to light, you are going to grow lots of algae, just keep that in mind.

A 5 gallon bucket of gravel as a filter. Hum that might be enough if you are talking about a system that has a lightly stocked 5 gallon aquarium as a fish tank. A 5 gallon bucket is not enough filtration for a system that would grow out eating size fish though. When using gravel as a filter, you probably need at least as much gravel as you have fish tank and even then, you need to keep stocking a bit light. Ya know, if you are going to use gravel as a filter, why not simply have media filled grow beds enough to grow plants in. Then you can add some NFT pipes being fed filtered water from the grow beds. Otherwise you will probably need some pretty darn good solids filtration and bio-filtration before sending the water to your NFT pipes.

With the big pipes, I still wouldn't bother trying to do anything like flood and drain, remember than when you cut holes for the baskets, the curve of the pipe will cause the holes to reduce the depth to which you would be able to flood, and a big pipe full of water is gonna get really heavy and could be a challenge to support. And having media just in the baskets won't really give you the benefits of a real flood and drain media filled grow bed.

Probably best to do the regular NFT thing and add wicks to the net pots if you can't find any net pots long enough (I use little yogurt cups that would simply have been thrown out anyway, I just poke holes in them.) The really handy thing about using wicks, is you can then simply start the seed right in the net pot against the wick and you don't need to go through the step of transplanting or top watering till the roots reach the water. Rayon mop string works well, cotton won't do it. Even if you don't want to put the seed starting right in the pipes, you can have a small tray of the net pots/cups with seeds starting (getting bottom water through the wicks) in a handy location while the previous crop is still finishing grow out in the pipes. I always found the step of transplanting tender little seedlings into the cups with gravel very tedious.

Why won't cotton work? Or maybe I should ask how did you know it wasn't working?
I'm using cheesecloth as a wick for some of mine, and haybaling twine for others. They both seem wet...

I'm using bits of old socks.. I agree they do seem to stay wet