I am a beginning diver, but a few years ago I purchased an AL19 that I use solely for checking regs before a dive trip and then soaking regs overnight after a trip. The AL19 fits perfectly in the bathtub, and I get it filled 1-2 times a year.
I am happy with this purchase and am confident it helps clean the regs. In hindsight, perhaps I should have purchased an AL40, but I was worried that it wouldn't easily fit in the bathtub or the closet, so from a size perspective, the AL19 has been good. I would measure the size of your container (or tub).
Or get one of these. I've soaked tanks as big as two LP108s in this rinse bin (i.e. cattle/horse water trough). I've had it for years. Incredibly durable.