I just ordered Darters . Imagine within 7 days will post pic as should have them by than.
The tank was originally going to be for cichlids but the current was so great with filter on side of glass that opted to go with darters and took tank apart and moved tank/stand to cold ac room in house lol.
http://www.monsterfishkeepers.com/forums/showthread.php?t=204166
I added more driftwood but kept same pebbles for tank bottom.
Either way I had darters yrs ago in 20 gallon long had variegated darters they did very well for yrs but never bred

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If your hang on filter moves enough water than no need for powerhead which can raise water temp a bit and you may not want that.
Some darters dont need current or very little .