I'm trying to improve the fish management in a private pond. I want to raise bass, bluegill and minnows. I had some rectangular pens made out of fine stainless steel mesh and floated them in my pond. A couple are 6'x6'x6' and one is 4'x12'x6' deep where I want to move the baby fish to as they get larger until I release them into the pond around age 1 year (the pond has an existing bass population and we are trying to introduce superior genetics). The guy who made them for me did not use all stainless steel screws and after a couple months in the pond some of the screws have rusted out and left some gaps where it appears about 2,000 1/2" baby bass probably escaped. I am rethinking the pen enclosure and I would like to line the entire pen (sides and bottom) with a fine aquatic mesh netting to double up my exterior and also make it easier to corral the fish when I need to check on them or move them.

I would need an aquatic rated netting that is fine enough to hold ½” baby fish, durable enough to remain intact in the water for at least a year and obviously breathable enough to allow proper oxygen to circulate. I want the netting to be in a single piece to limit the areas where it could come apart and I will probably need to be able to lightly brush off algae to keep the holes open for oxygen circulation.
Can you help me with this project or recommend a better netting solution?

I only know of netting that comes in 4' x 50' rolls. It's available in 1/8", 1/4", 1/2" and 3/4" mesh. It's plastic (not plastic coated steel mesh), and I have used it since the Spring of 2010. This is the 1/4" mesh stuff:

Welcome to PB.

Rigid plastic netting/fencing - do a search. It comes in all sizes , heights , lengths etc. It is used in offshore pens for fish raising as well as freshwater applications.

And it lasts forever! I've got some cages that are 10 years old with no problems. I do inspect them and do any repairs if I have to when I take them out once a year in the fall.

Where do you guys buy the plasic netting from?

I got mine from stoney creek out of Memphis Tn. I learned about them here on PB. I like their quality. I also learned late to use the black zip ties that are UV stabilized. The white ones are not UV stabilized.

I have built several this year and they are working very well for me.

Last I checked you could look online and buy direct from the producer (in rolls).

How do you guys feed the fish in the cages? Do you just place them in a broadcast area of an existing feeder, or do you feed them separately? I would like something like this, but I'm not always available for daily feedings.

Do you guys use one size or increase the mesh size as the fish grow?

One size 1/4 or 3/16.

Mesh size depends on length of fish. You want a mesh that the fish cannot get its head into. Mesh can be as small as 1/8" for 1" fish and as they grow put fish into larger mesh cages. I try to use the largest mesh possible to contain the fish while optimizing water circulation and minimizing clogging by algae.