I find a lot of fish are easy to breed, but the challenge comes in raising and maintaining good, healthy fish. Nothos tend to produce fair sized bunches all at once, and you have a lot of quick growers reaching adulthood in a hurry.
In many species, males spar or even fight, and you start to have serious losses in any tank. It's magnified in small ones. 40 gallon low tanks are generally called "breeders" in North America, but they often aren't for breeding but for rearing.
btw - I'm writing in response to
@Back in the fold , but I figure maybe new fishkeepers will also read this so I try to give context so it'll make sense.
If I get a good group from the eggs I bought, I'll have pairs in 5 gallon tanks, but will use a 30 inch 25 gallon for the main group. I don't know how many surplus fish I'd be able to find homes for. I used to keep Nothobranchius rubripinnis, and despite their being stunning little jewels, the annual reputation scared off club members. They aren't good community fish and the hobby is just starting to catch on to tiny fish in planted one species tanks again.
It really bothered me when the rubripinnis would whittle down their numbers, much like some Bettas (who also give you lots of young) do. In hindsight, I should have kept a group in large tanks, and had the small 5 gallons for spawning.
I used to live close to a US fish club, and would drive down once or twice every few years to visit the people and see the fish. The members (all AKAers) had tiny tanks with pairs of exotic Nothos, but I rarely saw fry. They would select their breeders, and what happened to the surplus fish was never discussed. They wouldn't bring fish to their exchanges, but only eggs. I don't want to do that, because these fish are a spectacle I enjoy. So unlike them, I'm planning on having my small tanks for breeding pairs, but larger tanks to keep groups. I'll collect and put aside eggs, as you must with these short lived fish.
The 'traditional' approach is tried and true. But I also want to enjoy more than bags of peat, and want to see these fish for the year or so they live. People who visited my fishroom with no knowledge of killies would stop dead in front of 3 tanks: my Chromaphyosemion biteniatum, my Aphyosemion striatum and my Nothobranchius rubripinnis. Most killies have beauty, but a lot of these little fish can stop you in your tracks from across a room (especially if you can play with light settings to catch the blue reflective scales).
I'd start looking at marketplace or online reselling sights and see what you can find in larger, used tanks. You only need an air driven filter in them, so the rest of the tech is easy. I hope to put 2 pairs aside from each Nothos species and use small tanks, just as I do with my Aphyosemions, and keep a 'reservoir' tank to watch the others interact and be fish. It really takes at least 3 tanks for each spawn of a Notho - 2 small, bare breeders, and one larger, traditional planted tank for the beauty of those you aren't breeding. Since groups do tend to time out at the same time, you time your hatches and move the new gang into the show tank to grow out when the old group has died off.
