If they are hunting at night, light does bother them, and sometimes they will leave a fish that they have killed mostly uneaten if you try to watch them with a flashlight or by turning on the light (learned that the hard way). If you do happen to catch your dragonfly feeding, though, you will undoubtedly be fascinated; it is unlike the feeding of any other invert I have ever kept.
I didn't have any problems with adult Dytiscus being housed together but I did keep them well fed.
I agree, I think diving beetles offer quite a bit more leeway when it comes to cannibalism. They seem to be pretty mild even when kept together in large groups (though I can't say what would happen with a sick/weak individual). I definitely lumped all aquatics into one cannibalistic group, but there's a big difference in keeping very active predators (like belostamomatids and nepids and Odonata nymphs) as opposed to scavengers or less aggressive feeders. Thanks for calling me out on that for clarity
I think a communal tank should be well filtered with lots of things for them to hang on to (based on what I've seen in the wild).
long-lived? How long are we talking. And does that include larval stage or adult stage? Beetles are some of the few homometabolous insects that I prefer the adult stage over the larval stage, but unfortunately most don't live long.
Thanks! With those considered, I may consider warrior and diving beetles lol! Warrior beetles intrigued me because they are like miniature tanks with ravenous tendencies- glad something like them gets the gift of longer life as adults.
diving beetles have no boundry on what they can consume,if it's edible,it's food moving or not,i have predatory fish,so they love the frozen silversides(a bit messy though) i had a group of them and when i put my hand in the water they attacked and they were really trying to eat my hand! kinda felt like little pinching all over,they are mini piranhas w/legs,they like turtle foodsticks which you can try and it's not messy,again they will eat an array of items,so you can try different things,the only problem i had is when i feed some superworms to the diving beetles i got from travis,they were dying off quickly,i was thinking stress,but also maybe there was a chemical the worms gave off in the water,possibly.i change the water once a week,ofcourse if ya have a filter that would help alot better,but they don't have to be in super clean water,being where they come from,swamps etc.you can feed 2x weekly for a single beetle,but if ya have more they would have to be fed more often ofcourse,and their larva,ah man words can't describe those beasts,hope this helps ya out alttle,oh and ofcourse alot of foliage to hang onto and some of it out of the water,sometimes they will dry out alittle,cover the tank too.