Your Bristlenose will love some Zucchini, Just put a slice on the end of a fork to hold it down. He also wants some driftwood. He will chew it to aid his digestion.
Unless the tank has been set up very recently there is no need to change water that often, once a week should be fine. Filter media can be rised many times before it needs replacing but be sure you rinse it in water you took from the tank. Tap water can kill the beneficial bacteria on the filter media.
The foam is protein scum and just happens. It may go away after awhile on it's own, (mostly), or if you get a filter with more surface movement it will keep it stirred up enough that it gets caught by the filter. either way it is not a big deal unless it covers the whole surface of the water and prevents air from getting to the water. You could run an airstone during the day to make it circulate and get trapped by the filter.
The fish will eat the worms.