Nicole,
Best of luck to you! I too have a whiskey barrel, which leaks. My first
water garden! YEAH! I tried a preformed liner, and long story, but yeah,
they don't fit to the bottom, and take away from the whiskey barrel look. I
didn't try a liner yet, as the leak is between 1/2 to 2/3 the way up the
barrel. We've had the barrel a long time, and it used to be water tight
(until we started filling it only 1/2 way). It SLOWLY is swelling. Some of
the staves are 1/4" apart. I'm hoping they will in fact re-seal. I'm
helping this process by setting an oscillating sprinkler on low and angled
just so, to get the edges wet for a few hours, and or, showering the whole
thing down on the outside several times a day.

I refill it every morning and evening, or so. The level IS moving up. The
plants seem fine- although I may have to raise some when the barrel gets
back to sealed. And when I did have fish, they were ok with the lower water
level, and I added conditioner every few refills (raccoons got them).

Anyway, that's my plan, to let it swell naturally.

But, plan B is to get some aquatic sealant and lower the water level to
below the leaks and then seal the puppy up. My family suggests when fall
and rain comes, all will be well, and to wait to do plan B. An extreme test
of patience, but one that may well turn out. I DO see some improvement- and
it's been I think 3 weeks now. (Wish me luck!!)

Keep us posted! I'm so thrilled to have another 'barreler!"