I honestly wouldn't put a Crawfish (large ones like Electric Blue, white or tangerine) in a 15 column. They like (and need) lots of space to roam and explore. The smallest tank id say they could be housed in is a 30 gallon, a 40 gallon breeder is an excellent size for them. NOW--> You could easily do a nice group of Mexican Dwarf Crawfish! They're awesome little guys that roam around and are awesome to watch! I'd definitely move the Goldfish out as they can get *very* large. If it's a comet goldfish then it will become massive! Other fish options you may want to consider would be: small Pencil Fish, some smaller Gouramis like the Licorice & Sparkling Gourami, Peacock Gudgeons, Badis Badis & Dario Dario. These look far better than Zebra Danios IMO but hey we all have our different tastes! Now you could only get some of these fish if you removed the Goldfish.
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