The main problem with the current pumps in a small tank is their lack of adjustability.
This is precisely what makes the Tunze's worth it - particularly the classic Nanostreams. The new 6020 is neat too though...I've been running one in my 50 gallon for a year or so.
You can do things with these pumps that aren't possible with most pumps that are either blinkered in "straight ahead" mode or that can only move a few degrees in any direction - like hiding them behind rocks
but still getting flow where you need it. Tunze even makes a ceramic "live rock" shell for almost all their flow pumps, so they can
really be hidden.
A pair of any of Tunze's smaller pumps, like the 6020's or the 6015's will give you better results. (The 6045 has manually adjustable flow for not
too much more money, if you'd rather spend on a pump that can go on to serve in a larger tank later on.)
A pair of 6015's ($40/ea) and a pair of appliance timers shouldn't run you more than $100. Running them so only one runs at a time and then switches every few hours to the other pump, gives your tank an awesome tide simulation that will make your corals HAPPY!
A pair of 6045's ($78/ea) gives you lots more flow to optionally play with.
The 6020 ($43/ea) is obviously different (flow is parallel to the mounting surface instead of perpendicular), but I still think you would just use two....mostly in the same setup. You just get very different flow patterns.
Adding a 6020 to a pair of 6015's would be good fun!
