Answers: No, you might want to drop the Clown Loach and the Gold Gourami. The Clown Loach grow over a foot long and your 30 gallon tank is no honourable place for an over sized fish. They also prefer to be in groups.Also, the gold Gourami grows about 6+ inches so its going to be a bit to big for that cistern. It also does not like to be alone and it prefers to be in pairs. If you want a Gourami, you can buy a Dwarf Gourami which only grows to roughly speaking 3 inches max. Always study fish before buying it so you won' have a fish thats to big, or a fish that's a bully and kills other fish. Also, another concern is the eel. It can consider your tetras or even chopper fish as meals.
the gouramis like to be kept in pairs and the clown loach should be kept within groups.
they are very social fish clown loach,
your tank would be to small for clown loach
go on www.aquaticlifedirect.co.uk