I don't know what your budget is, but I love my IQ5 Dymax tank. It's just under 3.5 gallons, and I keep a smallish female in it with a lot of plants and a few shrimp. The fish has plenty of room to explore/swim, never seems bored (hunting the shrimp really helps there, I think) and the tank has many good things about it.
- The filter is in a sump at the back, hidden behind a false wall. Downside is, you have to watch that the water levels don't drop in the sump, as the heater is housed back there too. I check that every water change, more in hot weather.
- It comes with inbuilt filter, lid and plant friendly LED light. Mine was sold without a heater (the adjustable Dymax mini heater fits the sump perfectly) but I bought the smaller IQ3 with one, so I think where you get it makes a difference.
- It's acrylic and light to carry, and a cube so has a small footprint for desk or bedside table.
- The filter pump is adjustable so you can reduce the flow easily.
Not the cheapest option, but I do love this tank and I'm very glad I bought it.