Shrimp can help a lot, but would get eaten by most of the fish you list.
Shrimp are best in a tank with small fish. The smallest of Tetras such as Embers, Dwarf Rasboras, Rainbows like Threadfins and so on. These are really better fish for that tank size, too. I sure would not put Goldfish in a 30 gallon except for a month or so while they are in quarantine. They can grow over a foot (30 cm) long in 2-3 years, 6" (15 cm) the first year. Angelfish are OK in 30 gallons, but when they pair up to breed that small a tank becomes all their territory, and they are likely to chase away or kill all the other fish in the tank. Angels can be predatory, too, eating fish like small tetras (Neon Tetras and smaller). You would end up with just 2 fish in the tank: The mated pair of Angels. And no shrimp.
I understand being on a budget, so if aluminum foil is the best you can do, it is better than some materials, but if you can paint the inside of the hood with a flat white paint that is one of the better reflectors. A clean, smooth paint job, perhaps a couple of coats, sanded between coats would be much better. Aluminum foil tends to go on with wrinkles, and is really not as good a reflector as you might think. There is the added problem that it can carry electricity. If there is any flaw in the wiring you could get shocked.
If the coral sand is going to stay, then I would look into fish that prefer somewhat harder water. Small fish that are compatible with shrimp: Asian Rummynose, Sawbwa resplendens is a good choice. The smaller live bearers like Guppies are usually shrimp-safe, too.
I do not see that it will be very effective when you put the denser material over the coral sand. The whole point of a UGF is that the water flows freely through it.
I have seen a way that this could work:
Section off the floor of the tank so that the front 1/4 is separate from the rest of the tank.
Put the UGF system here. Plates, coral sand or gravel. The rest of the tank has plant substrate.
Run the up-tubes to the back corners under the plant substrate, then up. The air bubbler would go in these the same as you have them now.
Maintenance is easy, since the only part that needs a deep vacuum is right in the front.