Complete newbie and clueless!

[plankton]

20ppm for nitrate is quite low, so don't worry about that.
Can you post pics of the damage? You have livebearers so it may be nipping, especially from the swordtails.
Melafix will help the healing process.

[Titchyfeep]

They are so hard to photograph because they are so fast. I’ve bought melafix anyway. The 2 red platys don’t seem happy at all. Staying on the bottom of the tank at the moment. I hope they are ok.

[Titchyfeep]

Sadly 2 red platys and 1 koi sword died. I should possibly have taken a photo after I removed them.The koi swords tail had developed a big furry fungus which I’m still assuming was fin rot but the 2 red platys didn’t actually look that bad. I still don’t know which of the fish gave birth and my husband watched the single visible fry getting eaten. I’m left with 1 koi sword which actually seems to have doubled in size since I got it and looks a picture of health and 2 red wags which do have damaged fins/tails but it’s not got any worse and they don’t seem unwell. My plants died AGAIN and I still think they could have introduced something in to the tank other than snails. My water is testing fine (details below) obviously I don’t want want to only have 3 fish but I don’t want to introduce anymore fish incase the 3 remaining ones are still contagious or it’s something else I’m missing. Kind of hoping I can get the neon tetras I wanted in the first place!

Not sure why I’m rambling on

Ammonia 0
Nitrite 0
Nitrate under 10
Ph 7.4
Kh 4
Gh 142.2
Temp 25°c

[black ghost]

You’ll lose the rest of the livebearers. Your water is too soft for them. They need moved to harder water.

[Titchyfeep]

You’ll lose the rest of the livebearers. Your water is too soft for them. They need moved to harder water.

Obviously I’m aware of that now and I’ve discussed it earlier in this post but what am I meant to do with them? I have no choice but to keep them and whatever happens happens.

[SPACKlick]

Not to overstate it but your legal duty of care to the fish obliges you to either adjust the parameters of your water (This is expensive and somewhat of a faff) or rehome them to suitable accomodation.

[Titchyfeep]

Well I don’t think anyone would take them because I can’t guarantee the fin rot is gone and if I took them back to the fish shop they would probably kill them and they wouldn’t be in any better water anyway. If I hadn’t come on this forum I would be none the wiser anyway and turns out loads of people keep platys in soft water and by all accounts they survive but don’t thrive. I obviously don’t want that but I do feel stuck with them.

[Chris_jennings]

Don't beet yourself up about it we all apart from the 'elite' have lost fish when we started out.

[Gingerlove05]

Don't beet yourself up about it we all apart from the 'elite' have lost fish when we started out.

Even the elite will have lost fish, everyone has to start somewhere. They just might not admit it

[VikingMummy2015]

You need a tub (get the smallest you can) of Seachem Equilibrium. Very gradually raise the hardness and remain with the fish you have. Hopefully they’ll survive and either naturally increase their numbers as livebearers do, or they’ll gradually die off over time. Or you can wait for the fin issues to resolve then add other fish which are suited to a wide range of water hardness (eg white cloud mountain minnows).

Once you no longer have dedicated hard water fish, you can then gradually reduce the hardness again back to natural water and add in soft water species.