Constipation can be caused by a lack of dietary fiber. Most flake or pellet foods are lacking in dietary fiber, so it is wise to give your fish other foods as well.
I personally supplement the diet of my fish with frozen brine shrimp, frozen daphnia, and deshelled cooked peas to help ward off constipation. If you have questions about how to prepare the peas, I can help or provide a link. They especially help, and if your fish don't want to eat them, you can soak them in garlic juice or get some SeaChem Garlic Guard.
Brine shrimp are also quite good, as is daphnia, which is probably small enough for Juniper to eat.
Just make sure you aren't overfeeding, as this can also cause constipation.
Another cause is pellets that take on water inside the stomach of the fish and swell up. To prevent this, it helps to soak the food in water before feeding.
Here's a link:
If it gets really bad, you may have to do an Epsom salt bath.