Wood is porous, it holds moister, fungus and mold spores. Even when painted it does not hold up to the elements. Aquaponics is a hot, wet environment; the sun is an intense heater. The wood is continually expanding and contracting, making annual painting a must.

It is extremely labor intensive to repaint these systems each year. With your system in production, it is near impossible to repaint without removing all of the grow rafts (where do they go while your painting). The grower must be overly patient and precise so not to drip paint into your ecosystem, possibly killing both fish and plants.

When painted each year the wooden system will decay, rot, crumble and attract termites as pictured above.
These systems rot from the inside out making it difficult to see the damage until it is too late.

These wooden components must be replaced after 4-6 years even when protected inside a greenhouse. With the laborious expense of building the system the first time, now it will be shut down (where to keep the fish) coupled with the labor cost of tearing down and disposing of the entire system while only salvaging the bulkheads. The next step is to rebuild the system again at a higher cost than the 1st time (inflation).

A simple math equation shows;

Build it once $ $ + Pay for it.

Paint and Maintain $ $ + Pay for it again.

Tear Down and Dispose of $ $ +Pay for it again

Build it Again $ $ = Pay for it again.

A wooden system may ultimately be the most expensive aquaponic system in the world.

It is said that only the rich can afford to buy cheap:
As they can afford to buy it over and over and over again.

Can you?