wood ash+galv. bucket+aquarium gravel=?

[glassbird]

I need a chemistry student here...

I gave my dad about 20 pounds of left-over aquarium gravel two months ago. He put it in a galvanized bucket and set it aside for some project he was working on. Just recently, I discovered that I needed the gravel back, as I am revamping my 75 gallon and did not have enough gravel. While pouring the gravel out of his bucket, into my bucket, I noticed that the gravel had a light dusting of dirt, or ash, in it. I rinsed the gravel repeatedly, and got the dirt/ash out out (finally), but the gravel has an acrid, burned smell to it. I asked Dad what was in the bucket, and apparently he has used the bucket to clean the ashes out of his wood stove.

I would think wood ash would not be an issue in an aquarium, in tiny amounts. (This is "coated" aquarium gravel, which I am thinking means it is not porous and likely to hang on to things.) But I know galvanized buckets contain zinc, and this is a bucket with visible corrosion on it. Is zinc a problem, in this type of situation? Could the combination of zinc and wood ash produce something toxic?

Ideally, I would give this gravel back to Dad, and buy new. But this is gravel that I have had for at least 10 years (and really like), and can not find more of it in my area. I am still looking online.

I took about three cups of it as a test batch, and have tried soaking the test batch in salted water (no change in smell). Then I rinsed it thoroughly, and tried baking soda (no change). Rinsed again, and tried diluted cider vinegar (some reduction in smell). My next tests involves bleach, and letting it dry in the sun, and then I will have run out of ideas! At this point, it is a challenge! Help!

 

[glassbird]

Well, the smell disappeared completely with bleach added to the water that the test batch was soaking in. I let it sit for an hour in the bleach/water mix, rinsed, and then added a hefty dose of Prime and let it sit. Rinsed, and smell is gone. I am somewhat encouraged, but still wondering if I have just killed the smell, and not solved the question of some chemical interaction, and possible toxicity.

I tested the water in the bucket with the main batch for pH (the main batch has been sitting in plain water for three days, and I used that water for the test). It was exactly 7.0. Also not sure that means anything. Then I added bleach to the main batch, and let it soak for 6 hours. Before I left for work, I rinsed it several times, refilled, and added Prime. In the morning, I will drain it all and let it sit outside until it is dry. I really can't think of anything else to do.

Any thoughts from anyone?

 

[BillD]

Sounds fine. Bleach would have been my first choice.