MR aquarium

salt will probably take care of it at that dose and the cichled should be fine.

this is a lot of damige over night it may have gotten stuck on/in something and gotten out at the cost of a lot of its fin i would think more a strong filter and he got to close maybe try putting a sponge on the intake of your filter and make sure he does not get infected

ph of 6 is very low if i were you i would raise that to 6.8 7.0 and i can agree with turning the temp down.

it looks like it is just a different colored part of its mouth from genetics and it does not look like an issue at all. if you do not just want to leave it then just keep an eye on it

the female also has shreded fins keep and eye on that. i would not worry about the spot to much just keep and eye on it it kinda looks like a scale is missing it may be a small infection or tiny parisite just keep an eye on it and you should be allgood.

in my opinion it sounds like genetics for that fish if you just remove them or cull them it should get better the person before you may have left bent spined guppys in and they bred and they gave you the good ones. this is just what i think and seems most likely to me.

i have kept corys for 5 years mainly pygmy corys and they are very hardy but if the ph gets below 6.4 (the lowest i have ever had ph) they start to act iritated but when i get the ph higher they are fine in my experience. so to me it sounds like ph.

Awesome pond those plants look so healthy and the water is so clear do you have a filter on there of is it all water changer air and plants?

the only thing i can think of after reading everything is that planting the new plants uncapped a bit of the soil and released something very deadly that does not give effects to a fish that are easy to see. guppy's in a lot of cases can be more hardy then cardinel tetras and plecos as you said can be bullet proof. yet this is the only thing i can think of on the spot i have no idea what could have been released from the soil. this is just my opinion of what went wrong this is my input to this interesting mystery.

if he is a very young/small cory then it could be possible that he got his fin lodged in the filter and it may have ripped of that is the only thing that i can think of for the cory getting stuck somewhere. as for being inactive i would say it is normol for a injured fish to be laid back and not move much i have had corys in all my tanks and that is the most likely things that i can think of. he should heal up real well if you keep water conditions good.

i anyone really just wants them gone and they wanna do it cheap i hear salt works really well with hydra for the reason that they have a very weak skin made mostly of water so they dehydrate fast. this is just my opinion and they will probably not harm fish at all if salt fails then you can go ahead and try what micks77 said.

it does not sound like anything that i have heard of it may have just been bad genetics if so you could have done nothing it will probably not spread if that is so. if it does spread then i have no idea what it is at the moment

in my opinion it would be a good idea to put the fry in a quarantine tank and treat them and keep a very close eye on the main tank and everything should be all good. this is just what i would do in this situation not what maybe best.