It has been working out fairly well, however, crossing an extreme branching betta against a smoothly rounded (lack branching) betta. The outcome, though not as satisfying as 2 extreme branching pairing in terms of its guarantee of getting all heavy branching fry, would deliver a very reasonable set of offsprings, all of which would be "acceptable" on branching. Sure, you may get SDs as well, but at least they're not too much prone to finrot as per rosetails....
The problem is in identifying whether a particular fish carries extreme branching or not. As with any other betta features, extreme branching is represented by a set of genes (or so we believe; isn't everything controlled by genes anyway?). So, what physically seen is not necessarily an indicator of extreme branchings. Some bettas don't show much of extremities, but when spawned, many of the offspring came out rosetail, for instance.
Our suggestion in regards to extreme branching:
- only cross a rosetail to non-rosetail
- crossing 2 feathertails are okay, however, make sure neither of them carry rosetail
- crossing feathertail to non-stable HM will improve the line, but also produce non-stability further (e.g. some SDs expected)
As for feathertail, good feathertail needs to occur towards the last set of branches making the tail looking very similar to bird's feather. If the branches started to form feather closer to peduncle and the tail becomes ruggerized, then you've got extreme feathertail. This happens when the fish has extreme branching (e.g. 16 or 32 rays) but the growth of the branch (further away from the main branch) is slower than the main branch.
Typically, extreme rosetail will have extreme feathertail. Some extreme rosetail can't even "close" their tail. Wherever they swim to, the tail will be fully expanded and non-collapsable! Serious caution when using this kind of fish, only cross them to non-rosetail non-feathertail fish, otherwise you'll get complete rosetail meltdown in your spawn.
The difficulty with both rosetail and feathertail is in the thin line associated in getting the perfect bettas. It has been a very long while since we're seeing good 32 or 64 rays branching fish, where all of its rays need to form full circle without much (if any) of ruggerised tail.
There are a number of variations with 220 degree fish. Some of them are the result of rosetail (hence you need to pay very close attention to their scale misalignment). Others surprisingly come from simple heavy branching, such as shown in this male image. You need to ask the simple question: can the tail collapse close when the fish swim? (The male pictured can collapse his tail okay). Pictures can't answer this unless you'd like to gamble in buying the fish. While non-rosetail gene that contributes to 220 degree fish is preferrable (for show, regularity in offsprings, etc), they are NOT contributing *much* to your offspring in terms of improving their finnage! In fact, you can treat them as if you're having a regular HM fish. This may come to a big surprise to some of you. Sure, you've got 1 or 2 fry coming out OHM as well, but majority will be regular HM. On the otherhand, if you've got a rosetail 220 degree fish, you're guaranteed to get OHM on most of the spawn and some minority of HM. Furthermore, about half of your OHM would be rosetail too. You'll only get extreme rosetail in the fry if *both* parentage carry rosetail (which is something you need to avoid -- as mentioned above).
So, hopefully this rumbling about rosetail and feathertail helps you a bit on deciding whether you'd like to introduce them into your spawn.