sealant for oak barrel fountain?

I have a couple of oak barrel fountains and I have inserted the molded plastic liners to keep them from leaking. These work great, but I don't like the way look, I would like to find a flexible sealant that I can brush or spray on the inside of the barrel. There is a catch; I would also like to be able to put fish in the fountain, so nothing toxic.
Anyone have any ideas?
Thanks! Steve
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snipped-for-privacy@gmail.com wrote:

Long ago I used to make wine in oak barrels. Once wet, they expand and seal themselves. But the reason that oak is used is because it supplies tannin which is an acid. I doubt that your fish will survive it. So some sort of pool sealer or basement glop or maybe, expoxy paint would be better than plain wood.
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how ironic, that natural way is toxic ;) Thanks for the information, I never thought about the taninsbeing a problem. I will also check into a possible additive to neutralize the acid, may or may not exist, but worth a check.
I would still be interested if anyone knows of a specific product that is non-toxic.
Have a good day and thanks for the response! Steve
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snipped-for-privacy@gmail.com wrote:

Well, if the barrel is intended for human as well as fish, i.e. an hot tub, the traditional wood is redwood. Be careful of splinters.
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