Anyone know about tropical fish??

What size tank? And when you say Harlequins, I am assuming you are talking about tetras (fresh water). Tetras are a little bit tricky to deal with like other tropicals. And yes, tetras are suicidal. I used to keep a bunch of neons, black neons, and serpaes. I don't know how many times I found little tetra corpses on my carpet the next morning when I went to feed them. LOL!

Gouramis are a little bit sturdier though. But you need to make sure you get a pair of Gouramis. But you also need to make sure you keep the tank clear of algae if your going to keep them in sunlight. Get a small algae eater for the tank. He'll keep the sides of the tank clean, don't put chemicals on the tank to keep it clean, it can do harm to the fish. And make sure you have a good filtration system as well.

The sturdiest fish I've ever had are fantail goldfish. I had one that lived for 2 years in a 10 gallon tank with no light. And he got HUGE!! LOL! I got him and a little playmate. LOL! All I did was feed him and his little buddy until his little buddy croaked about a year later. All they are are fancy carp. LOL! Those things can live in raw sewage. LOL!

Are you wanting to keep a salt water or fresh water tank? If you're wanting clowns, then you're going to need a salt water tank and they need quite a bit of attention!! Trust me! I've had salt, brackish, and fresh water tanks. But I'm going to assume that you're keeping a fresh water tank because you're talking about catfish. Yes, they are cool. And they are also helpful in that they are the little garbage disposals/ vacuum cleaners of the tank. LOL! I had two of them in mine as well. I called them Hoover and Eureka. LOL!

Fresh water is the best, especially if your only wanting to keep a small tank and wanting to keep it in natural light. If you're wanting to keep a salt water tank, the smallest that anyone will recommend is a 20 gallon but the salinity, acidity, and temp has to be very closely guarded in that.

You don't have to keep that close an eye on that with a fresh water tank and anyone can keep a decent 10 gallon tank going pretty well with good filtration. Heck, I did and I neglected mine for a couple days at times. And my 10 gallon tank survived for several years until I had to break it down when I went off to college. And I had to give away the fish I had. LOL!

Sniffer, you're talking about a Plecostamus. Those are algae eaters. The only problem with those is that they can grow to become over 14 inches long!! LOL! I had one that was only about an inch and a half when I bought him, but grew to be about 8 inches when I broke my tank down when I went off to college, and they are not fun to catch!! They are slow when they are meandering around along the bottom of the tank, but when when they are being chased, they are faster than a bullet!!