Hi Laura,
Since the weather is warmer you could haul the tank outside fill it with water the hose, and add a small amount of bleach. You don' t need a lot of bleach . ie If it's a 20 gallon no more than about 1/8 cup if bleach. Let it soak for some time ...then rinse. Caution: The bleach does the trick but is difficult to rinse. I re-fill the tank a few times and dump. Then after a few rinses ....ill again and add de-chlorinator-- ( lots of de-clorinator). Let it set for the de-chlorinator to work on any left over bleach. Rinse ,rinse ,rinse.

As for other tank decor:
Wood can be boiled or baked
Most hard plastic can be boiled ? - careful sometimes it disfigures them

If your comfortable with it ---you could even put things through the dishwasher including the wood ( no soap). Both the water and the drying cycle is real hot. BUT--- then you have to disinfect the dish washer But it works nicely.

Yes....the soaking dishes get really yuckie ! I clean 4 ( from the tree frogs enclosures) - every day! As for the soaking dishes ( and the walls of the tank ? if needed)- I use a very,very diluted solution of distilled water and Metronidizole in a spray bottle once a week. I spray both top and bottom , let them sit , then rinse. If you want the solution ratio let me know. ( my soaking dishes are ceramic flower pot saucers)

There are commercially prepared products, of which I have no experience with.

Lynn