New Platies seem sick

[DemoDrift]

I just recently got into fishkeeping, and my first attempt at a tank unfortunately resulted in my three guppies passing. This was in January.

I took a few months to research more and made sure to have my tank properly cycled. On February 23rd I had my water tested at the fish store and it was good to go. However, I waited until March 14th to get my mickey mouse platy. (They tested my water again and said it was fine). The platy was fine for all of Saturday and all of Sunday, so on Sunday afternoon I picked up an orange platy so that my first one would not be alone. I had my water tested when I got the second platy, and they said it was fine except for some slightly higher levels of nitrate than normal. The two behaved fine until I was preparing to go to bed when I noticed my orange platy swimming at the bottom of the tank at times.

When I woke up this morning, my orange platy was swimming at the bottom of the tank very close to my filter intake, seeming to get pulled towards it. When I fed them, only my mickey mouse platy ate food. Then, after about an hour, my mickey mouse platy began swimming close to the bottom of the tank and also seemed to get pulled towards the filter at times. As of right now, both are swimming close to the bottom, but neither are getting stuck to the filter intake.

When my guppy tank failed, it was because I had not properly cycled my tank. However, this time my platy tank's water levels tested fine.
I think that a 25 or 50% water change would be the smart option here, but is there anything else I can do to help them? How often should I change the water? They both seemed healthy yesterday, and I haven't even had my orange platy for 24 hours yet. I don't know why they are behaving like this.

My tank is a 5.5 gallon fresh water tank. Water Temperature is at 74 degrees Fahrenheit.

Thank you!

Orange platy swimming on bottom, Mickey Mouse Platy swimming in corner of tank.

 

[FishFinatic77]

Where did you get your water tested? If it was Petco or Petsmart, then they will tell you the water is fine even though it isn't. You should test the water again, then ask what all the parameters are, including GH and KH. The post them here.
The reason your nitrates were high is because platies need a much bigger tank. 5.5 gallons is really only good for a betta or some shrimp. Not much else can live in that size tank.
Your best bet right now is to get your water tested right away, then do a 75% water change. I would do a 50% water change every few days until you can rehome the platies and get a fish more suitable for your aquarium.

 

[JuiceBox52]

What is your GH?

 

[Colin_T]

As FishFanatic77 said, get the water tested and post the results in numbers here. If the shop says the water is fine, ask them for the numbers and write the results (in numbers) down when they tell you.

Do a 75% water change and gravel clean the substrate every day until you work out what is wrong.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

The fish don't look like they have a disease so the most likely cause is poor water quality or chemical poisoning.

Make sure you don't have any cream, grease, oil, soap residue, perfume or anything else on your hands when you work in the tank. Disinfectant wipes and soaps can leave a poisonous residue on the skin too.

Make sure nobody is smoking, painting or using any aerosols in the room.

Make sure you use a fish only bucket for the tank and not nay old bucket from around the house.

The orange fish looks like a gold molly, not a platy.

 

[Barry Tetra]

As FishFanatic77 said, get the water tested and post the results in numbers here. If the shop says the water is fine, ask them for the numbers and write the results (in numbers) down when they tell you.

Do a 75% water change and gravel clean the substrate every day until you work out what is wrong.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

The fish don't look like they have a disease so the most likely cause is poor water quality or chemical poisoning.

Make sure you don't have any cream, grease, oil, soap residue, perfume or anything else on your hands when you work in the tank. Disinfectant wipes and soaps can leave a poisonous residue on the skin too.

Make sure nobody is smoking, painting or using any aerosols in the room.

Make sure you use a fish only bucket for the tank and not nay old bucket from around the house.

The orange fish looks like a gold molly, not a platy.

Whats the difference between mollies and platies? They all look the same to me

 

[Colin_T]

Platies have a shorter body and only grow to about 2-3inches.

Mollies have a longer body and can grow to 3-4 inches for standard mollies (Poecilia sphenops, and 5-6 inches for sailfin mollies (P. velifera).