Zebra Danios possibly breeding?

[IndiaHawker]

I have four Zebra Danios - two appear to be longfin and the other two standard. I'd noticed for a bit that sometimes the two standard would chase the two (or possibly just one of) longfin. Not constantly, but for short periods. I suspect the two standard danios to be male, and I was previously thinking both longfin danios were female, although now I'm unsure if one is female and one male (pictures below).

About a week or two ago I noticed the two standard ones had really fired up yellow, thought something was wrong but looked up online and read that it's likely a positive thing and means they're happy and mating. There was a period around then in particular when I noticed more chasing than usual.

The chasing seems to have cooled off for now, but the zebra danio that I think is female looks like her stomach is a bit larger than usual - wondering if she could be carrying eggs? Read that the eggs aren't fertilized till they're released; is this correct?

Also on a related note, the longfin that I'm unsure about male/female has a three-forked tail - could this be from an old injury (got the tank secondhand with the fish included), or just the way it's grown? This one was swimming mostly at the top of the tank yesterday but appeared comfortable and not gasping for breath. Wondering if it's more likely a submissive male staying away from the others, or a female? I took some close-ups last night before turning off the light, and when I looked today it appears that the middle fork has possibly been nipped off or something's happened to it? However the fish if anything tonight is staying at the top of the tank less and doesn't appear stressed or being chased (although I'm not very knowledgeable yet so I may not be able to tell if the fish appears stressed) Here are some pictures that I took last night (before the possible fin-nipping):

These are the two that I think are male:

These four photos are of the one I believe to be female, and possibly carrying eggs:

And these three photos are of the longfin zebra danio that I previously believed to be female but now am unsure about - the first of these photos shows him/her next to a standard zebra danio that I think is male:

Please and thanks for any help!

 

[Colin_T]

Female danios are usually fatter than males due to the eggs they carry. Males are slimmer.

In the first picture there are 2 shortfin zebra danios and a red wagtail platy. The danio in the middle of the picture is a female, the one on the right of the picture is male.

The longfin danio in most of the other pictures is female.

The longfin danio with the damaged tail in the last picture, is a male. The damaged tail is probably from the other male. If it doesn't get infected it should be fine and grow back without any issues. Monitor the tail for red patches or lines, or white fluffy stuff or cream/ white edging to the tail.
Red is bacteria and white is fungus.

 

[IndiaHawker]

Female danios are usually fatter than males due to the eggs they carry. Males are slimmer.

In the first picture there are 2 shortfin zebra danios and a red wagtail platy. The danio in the middle of the picture is a female, the one on the right of the picture is male.

The longfin danio in most of the other pictures is female.

The longfin danio with the damaged tail in the last picture, is a male. The damaged tail is probably from the other male. If it doesn't get infected it should be fine and grow back without any issues. Monitor the tail for red patches or lines, or white fluffy stuff or cream/ white edging to the tail.
Red is bacteria and white is fungus.

Thank you for your help! Interesting, I'm glad I was at least right about the female longfin! How do you tell, because the females are fatter? Are you certain about one of the shortfins being female or could it just be the photo? I was so sure they were both male as they both fired up so yellow at one point and I read about males doing this - however you seem to have a lot more knowledge than me so I'll trust your judgement

Sadly as of today I can't see the injured longfin I can only assume he's passed which is a shame. The day after I he'd first looked nipped, I noticed more nipping - his tail was nipped back to a stub, but he was still swimming okay and I couldn't see any symptoms you'd warned me about, or anything at all - looked like a clean break. I actually noticed the platy possibly nipping his tail - although it seems more likely to be the other male danio considering the chasing behaviour I'd witnessed, could it have been the platy? Do you think what looked like a three forked tail could have been due to nipping, or grown like that?

Yesterday I took a rare opportunity whilst I could and went to the fish store to get three more bronze cories, as recommended for my poor lonely Dory. They seem to be having a great time together and I believe I purchased well as all of the fish in the store appeared well-looked after and healthy, obviously including those in the tank I bought from. However I'm now left wondering if this could have somehow caused the death of the danio? Stress from the new tankmates? Or possibly the high pH and nitrates present in my tap water as mentioned in a recent thread and will be sorted at the end of the month. Or possibly the fish got more injured whilst I was asleep and didn't make it? I haven't yet been able to find the body - as seems to be a pattern in this tank

Please and thanks again!

 

[Colin_T]

Female barbs, tetras, danios and goldfish all have fat stomachs compared to males. This is from eggs developing inside them. Female fish also eat more compared their male counterparts but it is not always that easy to tell. But if a danio has a fat belly it is female (assuming it is not dying from an internal infection). In your photos the fat ones are females and the males are the skinny ones.

If the fish has an internal infection they suddenly get fat (usually overnight), their scales will sometimes stick out from the side of the body, the fish stops eating and sits in a corner somewhere waiting to die. Your fish do not have that issue so there is nothing to worry about in that respects. I am simply putting this here because I mentioned "internal infection" in the previous paragraph.

-------------------------
The 3 pointed tail is probably from damage.

The platy or the other male danio might have been nipping the tail.

As a general rule, if you want long finned fish, then only keep long finned fish. Try not to mix short fin fish with long fin fish, (eg: no short fin danios with long fin danios). The short finned fish can move faster and out compete the long finned fish and problems can arise. I wouldn't worry about the short fin male you have left, but in future try to get all long fin or all short fin.

-------------------------
You should check the aquarium for the body. It could be under plants, rocks, wood or stuck on the filter intake. If you have a dead fish in the aquarium, it can produce huge amounts of ammonia that can poison all the fish. You need to find and remove the body asap.