What would be the smallest dimensions for an adult of one of the more commonly available rays (feel free to suggest the best one for a beginner) I'm faced with the choice of either doing an outdoor pond next spring or an indoor pond next summer and if I did an indoor pond I'd go fairly large and do oddball fish such as rays and gars (two fish that really got me into the hobby I've been wanting to keep for years). I've wanted a ray for a while now but my biggest tank now is a 75 and that's nowhere near big enough for any adult of the Potamotrygon genus obviously.