I have several newbie questions that I'd like to throw out, and see what I can get for information.

a) How many killifish would a 100 gallon stock tank support? I know this is a very general question but I'm just looking for a rough number of fish that could be housed in there. My mindset is still in the gutter, based around how to stock African cichlids into a tank. Do the fish like to be crowded or to have a lot of space?

b) Am I limited to one male of each species in a environment that size? I've watched some of the Fundulus dispar here in our backwaters chasing each other, generally males chasing each other. I would like to keep a couple males of each species of killifish that I might acquire but don't want constant beatings on weaker males (like cichlids can do if stocked improperly).

c) Can I have too many females? I'm not sure how aggressive females are.

d) Do killifish set up "territories" or are they a free-roaming fish? Not sure if males/females just lay claim to certain space and chase of competitive males.

e) Generally speaking, how is the conspecific aggression compared to contraspecific aggression? Do males/females only chase off their own species or do they bother other species as well?

Any help would be great. These fish are so foreign to me but would like to build a home that's comfortable.

I don't know about most killies, but for a fact, blackspotted topminnows will kill each other off until only one is left. Kind of surprising since you always see them travel in packs in the wild.

I love Killifish but I'm no expert. Please take my information with a grain of salt.

a) difficult to give a number since the amount of water changes (if any) and general care (filtration etc) are really the determining factors in the number of fish you can keep. Are you talking about a species only tank? If your willing to filter and change water, I'd guess 50 fish would be no problem.

b) Male aggression can be intense and prolonged. I have to admit that F. dispar can be rather nasty during the spawning season but out of season are much more subdued. Other Killifish in my experience exhibit quite a lot of chasing and even fin nipping in the spring. In cramped conditions this can be severe. High male/female ratios contribute to the problem.

c) Females are calm compared to males. They tend to stay out of the mess that males create during this time of year and don't seem to harass other females to any real degree.

d) Good question. I'm not sure to be honest. I get the impression that males simply seek receptive females and make themselves available wherever and whenever while making sure other males stay well away. This is based on casual observations of fishes at home.

e) There are good mixes and bad. F. chryostus males in spawning mode will attack just about any fish but especially other killifish. If you remove the female the aggression usually subsides shortly. F. lineolatus and F. nottii males can get a bit nasty from time to time without real spawning going on. Same holds true for F. notii/F. blairae mix & F. olivaceus/F. notatus mix. I guess this is due to the similar appearance but might be due to other factors. I can say that I have very little issues when I keep males of dissimilar looking Fundulus together. I mix Fundulus in my display tanks for the family and would suggest it to you as well. Just stay away from very similar fishes in the same tank and all should be good. You can always experiment as long as you have room to separate potential problem fish.

I hope this is helpful and I hope others can expand on this information. I have much to learn about our native killifish.

Thanks for the help so far.

Waterchanges aren't a big deal to me - I used to do waterchanges every other day on my cichlid tanks (55 Gallons). And with raising African cichlids I know the importance of hiding spots, so I plan to heavily decorate the tank.

I would like to steer clear of a species only tank - as I like variety.

I don't know about most killies, but for a fact, blackspotted topminnows will kill each other off until only one is left. Kind of surprising since you always see them travel in packs in the wild.

That's weird... I thought they would be fine together in a tank since I always saw them in packs in the water and I've got 1 male and 1 female (I think) and they've been doing fine... no aggression whatsoever. I would never have guessed that these fish weren't perfect community fish. Maybe it has to do with the way my tank is planted?

I've never had aggression with blackspotted topminnows. In my experience they hang out and look a little cagey, but I've never seen one attack another. I'd think that a dozen could easily be kept in a 100 gal. tank, with other fish such as shiners living in the mid-water column.

I've never had aggression with blackspotted topminnows. In my experience they hang out and look a little cagey, but I've never seen one attack another. I'd think that a dozen could easily be kept in a 100 gal. tank, with other fish such as shiners living in the mid-water column.

Oh... I just noticed that you said blackSPOTTED. I have blackstriped. Sorry :S

How often should fish be fed? Once a day? Every other day?

Right now my tank doesn't have a heater in it so the water is a bit cool (to the touch) so I figured the fishes' metabolism would be a bit slower. I've thrown in some New Life Spectrum Cichlid Pellet and some HBH 8 Veggie Flake in there for them to eat if they wish.

Oh... I just noticed that you said blackSPOTTED. I have blackstriped. Sorry :S

Yeah, I've heard that blackstriped (F. notatus) are more aggressive than blackspotted (F. olivaceus). It's an interesting difference since the two species are so similar in most ways.

Yeah, I've heard that blackstriped (F. notatus) are more aggressive than blackspotted (F. olivaceus). It's an interesting difference since the two species are so similar in most ways.

Well, regardless - I guess going into my tank is the kiss of death for either...

I have mummichog killies,siminolie(sorry any native americans cant spell)blackspotted,blackstripe,and a lone eastern starhead for agression blackspotted seemed to be the most aggressive with mummichogs in with feeder fish a close 2ed(think its odd how people think them as alage eaters)
I have all the topminnows and the eastern starhead in a 20long (13 fish in total) with no aggression related deaths at all they nip fins but not to a fungus level