Wood preservative

How about a coat or two of polyurethane varnish?

The only thing we ever did with wood for aquariums was to boil the ever-lovin' heck out of it to kill any pathogens. Once in the tank, the wood aged as it would in the wild.

As someone else pointed out, you could also cover it in plastic.

Thank you for the indication about boiling the heck out of the timber. In certain parts of Indonesia and the Pacifc Islands (only for bamboos), they make sure that it is cut at the time when the sap is lowest ( I do not remember exactly at which phase of the moon), subsequently the quite large bamboo sticks are left floating in sea-water for about six weeks.

This was the natural way of avoiding pests thereafter. Hope this may be usefull.

Labor Omnia Vincit.

Polyurathane varnish is a good coat. There are also paints with PU as a base with UV and othe protection with pigments added. One of the brands is Alocit. You can paint the wood with Alocit paint also. Anything PU will be helpful

Go with the polyurathene, 2 or 3 good coats then submerge in clear water to test for voids / uncovered areas. Touch up as required

Good luck

You could look at the WEST system: WET EXPOXY SATURATION TECHNIQUE sold at alot of boating stores. Works well on natural wood hulls submerged in water.

www.mectorrefaction.com or equivalent, then epoxy impregnation www.westsystem.com use the 207 for clear wood grain show. we used the 207 in our algea removal trailer and it resists very well the beating (water, algeas, fork shovels , stones, etc) and it is easy to restore .

The people who make POR-15 paint also make a product called Glisten PC, a 2 part urathane (Im assuming) epoxy paint that many people use on boat wood work. It dries clear, and very hard. I use it to clear coat things I've painted in the past. Also, its pretty thin in terms of viscosity, so you should have no problems getting into all the holes and crevices.

I don't know the size of your wood or your access to equipment or funds.

Given that pull a hard vacuum on the wood and inject aquarium silicone into and on the wood. Once dry it should last a long time and be as benign as the seals in your tank. Messy but wipe it down with a rough towel or rag before drying to get the surface of the wood. This should also make it weigh enough to sink.

Just an idea

Bad

Go to www.preservation-solutions.com

Use an S1 sealer or clear liquid epoxy.

Whatever the brand , it needs to be liquid enough to soak into the wood. Recoat a few times, but before you do ,be sure to wipe off the amine bliush, (a light oily film that occurs after the epoxy has cured, removable with a warm fresh water wipe).

Other finishes like the polys...will not hold up under water!