So, this post will just be an introduction to my project.

PROBLEM: I have a nice piece of driftwood that will not sink
PROPOSED SOLUTION: Boar out the wood, create concrete plugs to hammer into the wood to weigh it down

RESEARCH: Concrete is very alkaline in nature do to the "setting" ingredient cement(made of lime). When not cured it will leech lye and can be harmful to fish, drastic increase in PH. After being properly cured it will not leech into the water column. Some good tips I have read are to try and find Portland Cement Type III(Smaller particles and some other good reasons), use just the bare minimum amount of cement to make other materials(Sand, Pea Grave, etc) "set". I have read if you fire(kiln,fire,grill,oven [TBD in this project]) the cast concrete it speeds the curing process. Soaking and monitoring the PH in a bucket/tub with water changes as well, best water to use for this is slightly acidic and soft. Have read of some people soaking the concrete and adding anywhere from house hold distilled vinegar to Muriatic acid. Plus, the old rule of quantity/volume; i.e.- since I will only be using about 20-25 cubic inches inside of wood(eventually) in a 120 G the fluctuations would not be to drastic(Hoping).

Apparently, they use concrete in a lot of pond setups, especially in Texas. Basically, most companies leave these baking in the sun for long periods of time, sometimes even filled with water(with changes of course) to cure them.

Well, here is the outline of the project. My buddy and I that will be working on this are currently converting his carport to a garage. Meaning, my project will be a while before some solid progress.

I don't think there is any problem with using concrete in the aquarium.

However, I'm not sure if it will actually cause the wood to sink! Depending on how buoyant the wood is (if you hold it underwater at the bottom and let go, does it launch itself out of the water?) the weight of the concrete might not be enough.

I'd screw it into slate, or lash it to a rock or two.

I haven't actually put it in water yet, I bought it from Brian after the cookout. I believe he said he was using about 20-30lbs of rock to weigh it down. I was thinking since sand and concrete range from .90-.97 pounds per square inch if I filled it 20-25 cubic inches it would way approx 18-24lbs. Plus I believe the holes I have drilled out have taken away from the total buoyancy.

I like the slate idea but then we are stuck with it in that position. This is just a project I thought I would try out and see how it goes. I am hoping for the best and it may take more time and effort than the slate, we will all see in the future I guess.

If this is something of an experiment then I think you should feel safe to try it. Unless you are keeping very delicate soft-water species that require blackwater acid conditions, you won't have any trouble from a bit of extra buffering in the water.

Concrete actually cures better under water than in the air, so don't worry about that part of it.

Please keep us posted!

honestly, i just got a nice sized piece of driftwood as well and wired it to 3 big rocks and it sink perfectly fine. these rocks were HEAVY though... lol i havnt heard any bad results about concrete in a tank. it might raise your pH and ad minerals but thats not usually a bad thing

I make all my backgrounds and caves with mortar and mix it with old gravel. I soak it in water for a few days and drain the bucket and soak it again a few times. The background will raise the PH to 9 but the cichlids don't mind. The PH will drop on its own. Doing a couple water changes will help. I haven't any fish problems at all.

Now I dont know to much about concrete. But I did read about your nice piece of driftwood and how you didnt want to have it in a fixed position my anchoring it down with a piece of slate. I got a sweet piece of driftwood from 2 meetings ago. the wood was all dried out. I soaked it and it would shoot up to the top of the tank. So what i have done is placed 3 nice heavy pieces of slate on top of the driftwood to make some great hiding places. I didnt zip tie or glued the slate in place, because i still want to be able to switch it around and still try and give it a somewhat natural look. Plants around the driftwood also helps with the look. I know its a different way of doing it, but I also hopes it gives ya a different option, or another way of giving you what ya want without any limitations.

Sweet thanks for all the input guys! Any little bit helps!

also, with the driftwood, i've heard boiling it works. now depending on size of your wood this might not be possible lol, but when you boil it, it forces all the air pockets on the inside of the log outward which thus cause it to become water logged