Hi
I have a couple idea's for you, I don't now if they will be helpful or not.
Could you maybe hand make a platform of some kind with legs attached that would raise the tank up a little off of your radio, but still be in that space you have?. I don't now if your radio has a boxed in frame for it or what, it is still hard to picture the size radio in my mind.
Second idea, if the first one isn't feasible. You could think of coming up with a time frame as to when you will and won't play your radio. For example - you know that they sleep during the day and are awake at night, so plan several hours in a row during the day when you won't play your music, so they can have some good uninterupted sleep time, and then when you do play it, just don't play it real loud and maybe tone down the base when you do.
Don't now if this will help you or not.
Take Care, TLB