Paradise Fish are fun to watch, colorful, and intelligent. They will come to your fingers for food, even sometimes jump to your fingers for food if held a little above the water surface. Like Bettas, they can be kept in bowls, but a very large bowl is needed since they can get about 10 cm. A 20 L tank is best if kept alone, in my opinion. Paradise fish need a lid! They like to jump out on occasion and explore your floor. If kept alone, a paradise fish should be exercised with a mirror daily just like a betta. The displays aren't as extravagant as a betta's, but just as entertaining.
I bought a blue paradise and placed him in community tank with gouramis, catfish, mollies, guppies, danios, ghost shrimp, snails, darters and a female betta. He didn't initially fight with the other gouramis. Actually, all 7 gouramis (including himself) stayed together. He was generally well behaved, considering how I had seen others act towards their own type. Anyway, I noticed a few days later that one of my cories was missing an eye as well as a danio, but didn't think much of it. Later, when I moved the aquarium and replaced the female betta with a male, the paradise ripped his nice fins to shreds in less than ten minutes. I was rather upset, since this was a black betta which are rather hard to come by. Anyway so I separated both and the betta's fins are growing back. Since I placed the paradise in a bowl alone he seems more timid, yet more aggressive at the same time. However, for the most part I didn't have much trouble out of him, he was actually one of the more responsive fish in my community tank.
I keep a black paradise alone in a 110 L. He is probably the most violent fish I have. When I added a hillstream loach (I keep him at room temperature) he, as you might expect from other comments, proceeded to eat its eyes out the minute I walked away. I returned less than hour after introducing the loach to find it quite dead and eyeless. The Paradise greeted me proudly. He shows great red on his ventrals, which intensify with regular live food. I don't show him a mirror, which might be part of why he hides a lot...I really don't know, and I doubt I will ever see a female black, so he will be a solo fellow unless something tells me he desperately needs company. He will not touch any food lacking in protein, but gladly gobbles up (slowly) any flake or pellet food, or mini-mealworm, etc. Great, easy fish to keep, and pretty when they want to be.
Looking for a more energetic alternative to bettas, I bought 3 male paradise fish and put them together in a roughly 12 liter bowl. Big mistake! I don't know what the girl from the fish store was thinking, but I had them together for about 3 days before I could tolerate the chasing and fin-nipping no longer. Now they are separated to 3 different large apothecary jars next to each other. They'll catch a glimpse of one another and go have a display-off. These paradise fish absolutely love to jump, so a lid is important. Percival and Friday get excited when anyone enters the room, and if you put a finger on their clear glass lid they'll try to jump for it! They are so full of personality, they are my new favorite fish! I also made the mistake of trying to keep 2 Japanese Algae Eating Shrimp with one of my paradise fish and let's just say I don't recommend it - he chased them around and around until they hid under a rock and refused to come out. He does, however, get along with Dolores the golden apple snail quite well. A very hardy, colorful, and animated fish.
It's now been only one week since I got my pair of paradise. Two days ago I was delighted to see my paradise have layed eggs! The male was guarding them in his bubble nest. As there were some notorious barbs in the tank, I decided to move the eggs into a separate tank with the male, but I wasn't able to get the eggs without breaking the bubble nest. I was worried whether the eggs would survive. But I was amazed to see after some time the male is building the nest again! He took eggs into his mouth and spit them out with his saliva. Several hours later there was a nice nest filled with eggs. Now I'm waiting to see the hatchlings.
These pages have enough comments to give the reader a basic idea on the topic. Further comments are still very welcome (through the site's contact form) as long as they provide new and/or advanced information not yet discussed in the existing ones.