watch for stress; find out if they are "schooling" fish; possibly separate them, or get a larger tank
Separate them as much as possible. If not possible, add more decorations and plants for more territories and feed them.
A water rocket should probably have three to four fins.
Dorsal fin, Flukes on the tail, and Pectoral fins on each side
The pectoral fins(located on each side) helps steer a fish during movement.
There are two sets of "paired" fins. The ones on each side of the fish behind the gills are the "Pectoral Fins" and the ones in front of the fishes vent on the underside of the fish are the "Ventral Fins". Sometimes these fins are wrongly refered to as "Pelvic Fins".
The pectoral fins(located on each side) helps steer a fish during movement.
Geometry Five dierent n geometries are available. Geometric dimensions to be specied for each fin type are Straight Fins Annular Fins Longitudinal Fins Rectangular Fins Conical Fins Trapezoidal Fins Parabolic Fins Cylindrical Fins/Pins/Spines Truncated Conical Spine Triangular Fins
get more of them so they'll even out there aggresive behavior on each other
Often fish will 'nip' or bite off parts of the fins. Or you may have fin rot. If you only have a few (3-4) fish, they may be eating each others' fins. If your fish look sick, they need to have some medicine. Or if they are being kept with other fish or crabs or crayfish, they might be losing fin to them.
Two fins - placed exactly opposite each other - will still allow the rocket to 'wobble'. Three (or more) fins equally spaced provide stability.
The tail or caudal fin is attached to the spine. The others are attached to muscles.
3in