Red Platy fish lying in the corner. Help!

I have a 10 gallon tank, with 1 halfmoon betta, 3 molly, 1 mickey mouse platy and one red platy(I don't know which species she is, her eyes are red though)
I've had this tank for around 4months now. I cannot buy ammonia or nitrate or nitrite testing kits as of now so cannot check them either. But I do weekly water changes of 50%
Since last 2 days my red platy has been lying at the bottom of the tank, she doesn't come up during the feeding time either. She doesn't seem to have any white spots or wounds. She just lays in a corner, her pectoral fin moves all the time and she has rapid breathing.
When exposed to phone light she tries to run away but it's like she has gone blind cause she keeps hitting things while trying to run away. It's not like flashing cause she doesn't do it all the time but only when exposed to flash light.. she doesn't swim up either. Just stays at the bottom. But when the aquarium light is on she curls up further into the corner. She does move though. If some other fish goes near her, she would glide away but won't swim up.
Can anyone tell me what her ailment is? And how I could treat her?
P.S. I'm attaching a picture of the platy. See if that helps.
P.P.S. I had kept the lightning cycles to 8hours lightning. But I had reduced the lightning to two hours per day to descrease the algal growth. She has been showing this behavior ever since then.

P.S. The platy seems to be drooping to her left side and her left fin stops moving every now and then, unlike the right fin which moves all the time.
P.P.S. My betta seems to not like the platy. I don't know if the nipped it's fins but the betta went after the platy whilst I was taking pictures for the forum.

Most bettas don't like sharing their space. If the betta went after the platy while you were watching its happening all the time and you will end up with a dead platy - and probably more deaths along the way.

Your tank is too small for platy or mollies anyway so these should be re-homed ASAP. The platy has clamped fins which may indicate a water quality problem as well. Do a 75% water change.

Wipe the inside of the glass down with a clean fish sponge.

Do a 75% water change and gravel clean the substrate.
Make sure any new water is free of hlorine/ chloramine before it's added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. Wash filter media/ materials in a bucet of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn.

Add 2 heaped tablespoons of rock salt, sea salt, or swimming pool salt for every 20 litres of tank water. Keep the salt in there for 2 weeks. If you do a water change while using salt, add salt to the new water before adding it to the tank so the salinity (salt level) in the tank remains constant.

See how the fish looks in a few days and if no better post more pics and a short video of the fish.

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Add some plants if you don't have any. Plastic or real, real is preferable but anything is better than none.

Make sure you have a picture or something on the back of the tank to make the fish feel more secure.

Remove betta asap, betta are not community fish and should not be kept with other fishes, they are aggressive, territorial and sometimes even kill all of your fishes.
As for swordtail you should add salt that Colin already stated that above.

In 10 gallons it would be better to remove everything else and leave the betta in the tank alone. It's too small for platies and mollies.

seangee said:

Most bettas don't like sharing their space. If the betta went after the platy while you were watching its happening all the time and you will end up with a dead platy - and probably more deaths along the way.

Your tank is too small for platy or mollies anyway so these should be re-homed ASAP. The platy has clamped fins which may indicate a water quality problem as well. Do a 75% water change.

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I did a 50% water change 4 days ago. Are you sure I should continue with a 75% water change?
P.S. As you know it is impossible to buy a new tank as of now. Is there any other alternative?

Artee said:

I did a 50% water change 4 days ago. Are you sure I should continue with a 75% water change?

Click to expand...

Yes!

Colin_T said:

Wipe the inside of the glass down with a clean fish sponge.

Do a 75% water change and gravel clean the substrate.
Make sure any new water is free of hlorine/ chloramine before it's added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. Wash filter media/ materials in a bucet of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn.

Add 2 heaped tablespoons of rock salt, sea salt, or swimming pool salt for every 20 litres of tank water. Keep the salt in there for 2 weeks. If you do a water change while using salt, add salt to the new water before adding it to the tank so the salinity (salt level) in the tank remains constant.

See how the fish looks in a few days and if no better post more pics and a short video of the fish.

-----------
Add some plants if you don't have any. Plastic or real, real is preferable but anything is better than none.

Make sure you have a picture or something on the back of the tank to make the fish feel more secure.

Click to expand...

I did a thorough gravel cleaning and 50% water change 4 days ago. The substrate I've used is sand and it was full of brown algae and small white worms, hardly 1cm long and as fine as hair. I didn't remove my fishes whilst doing substrate cleaning, am I supposed to remove the fishes?

Around 2 months ago I had another betta who seemed ill when I bought him (I thought I'll somehow nurse him back to life) but he showed symptoms of ick and I isolated him to a 4Litre container and added a bit of rock salt and ick treatment. The betta died within one hour since addition of salt. Are you sure I should continue with Rock salt? Maybe Epsom salt would be a better alternative (which I do not have as of now)

I did have real plants. Amazon sword, anubias nana, duckweed, elodea and a purple plant. Only duckweed and anubias survived. Even those are starting to die. Anubias has little holes which I realize are done by snails that came with elodea's plants. There are too many snails now and I don't know what to do with them (we don't have a garden to relocate them to (I do know places I could leave them at, but I'm stuck inside since 3 months)) I even added liquid CO² supplements and mineral supplements but I don't seem to have luck with aquarium plants. I looked into fake plants but most of the trustworthy brands do not deliver in India. If you know a brand that delivers in Mumbai, India please do let me know.

seangee said:

Yes!

Click to expand...

Thank you

essjay said:

In 10 gallons it would be better to remove everything else and leave the betta in the tank alone. It's too small for platies and mollies.

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I do not have a spare tank as of now to move the mollies and platys into. I cannot even go out and buy. Is there anything else I could do? They seemed to be doing well together a month ago, at the time there were lots of plants in the tank and I think it made a good hiding spot back then. Thank you for your response.

The worms in your tank mean it is very overstocked and there is a lot of fish poop or uneaten food in the gravel.

Epsom salt is only used as a separate bath when a fish has dropsy. Ordinary salts is for treating infections in the main tank. It should be pure salt - the kind of salt we use for our food usually contains anti caking agents and in some places it also contains iodate. Any salt with these additives should not be used. If rock salt is pure, it should be OK but if it is not food grade it could have all sorts of other things in it.

It is possible that the other betta was so sick nothing would have helped, and perhaps you added too much salt for such a small container - you only need 1 x 5 ml spoonful (teaspoonful) for 4 litres.

If you need something to move the other fish to use a food safe plastic tub. Add an air stone for oxygen and a heater if you can

Just letting everyone know I couldn't save the platy. Sadly she passed away 4days ago. I did the 75%water change amd cleaned the gravel thoroughly (there was a lot of poop). The rest of the fishes seem to be okay and healthy even though they don't eat as much as before. Anyways thank you everyone for your help.

There are too many fish in this small a tank as already noted, but in the short-term there are things you can be doing while waiting for the necessary solution which is removing these fish to other tanks or the store.

Reduce feeding. It seems there is a lot of detritus building up, so less food in means less waste out. Feed sparingly, and every other day won't hurt. Do weekly 70% water changes and clean in the gravel thoroughly at each, and keep the filter well rinsed. All of this reduces organics.

See if you can find out the GH (general hardness) and pH of your tap water, check the water authority's website or call them. We don't have this data, but livebearers like platies need moderately hard water and if the water should be on the soft side they will slowly weaken.