I have a 6" JD in a 55 gallon. I've heard some say that one JD can be kept in a 55, others that a 55 is too small for an adult JD. Does anyone think that there can be tankmates like dithers. If so any suggestions?
A 55 is pretty small.
In nature JDs share habitat with velifora mollies, and some other live bearers.
Because the livebearers normally live near the surface, and JDs prefer areas near the substrate, if the livebearers are large enough, there is a possibility of coexistence.
And although JDs prey on livebearer fry, they seem to not feel territorial threats from the adults, and in nature seem to miss 9 out of 10 strikes. In the confines of an aquarium, the success rate would be much higher https://www.youtube.com/watch?v=txmi1mng_XQ https://www.youtube.com/watch?v=e8OVy3JKxcw
When a pair of JDs spawn in nature they seem to protect a 4 X 4 X 4' area from other cichlids and catfish, if the terrain allows. I have also seen them protect long narrow corridors.
4x4x4 I believe is almost 500 gallons.
The male on the right, is protecting his territory, the space looks small but it is about 4 ft deep, and he is large, probably 10".
Note both their lips are white with scars from jaw locking battles