+1 to Carey and Rookie on canister filters.
You do have goldies in this tank I believe and that's an option to consider if your budget allows for it. As Carey said Fluval is a good choice that has a model 205 that would work (305 more so) and would be something I'd recommend. As I said, it is a much higher price point, but it would certainly do the job. I have the 305 on a 29g GSP tank and I love it for how well it cleans, media setup, and ease of use (AKA it's easier to clean/service than my HOB