Platy swimming at top of tank head up, very frantic

[BOBJOESIM]

Hello,
I've been keeping platies for the last 5 months, started out with 7 and some died along the way. One seemingly was weak from the start, and got REALLY bloated to the point that all the scales were raised on his body and he died. I didn't have any problems except after 2 months where two of my platies died out of the blue...no symptoms, ammonia at zero (do not have a testing kit for that but I believe since my aquarium is well planted it should take care of it), well oxygenated water (plants and airstone), heater at 78 degrees, and feeding flakes everyday, sometimes bloodworms. Today I noticed one of my platies swimming quite a lot at the surface (not all the time but a majority), she seems to have lost some weight however her stool is perfectly normal. I also noticed one of her top fins seemed a bit damaged (a little indent, looks like something from a nip), and her belly is a little whiter than usual, although I'm not sure if that may be because of her loss of weight. She does eat however, perhaps not as much.

 

[BOBJOESIM]

 

[BOBJOESIM]

 

[FroFro]

First off we need to know your water parameters
Nitrate, Nitrite, Ph, Ammonia, alkalinity.

Secondly, you feed them every day? How much a day, just a pinch or enough to have food float to the bottom? Do you vacuum the gravel to get any uneaten food/poop? Having plants doesn't mean an instant cycled tank.

 

[StevenF]

ammonia at zero (do not have a testing kit for that but I believe since my aquarium is well planted it should take care of it),

If your water has all the nutrients, especially micro nutrients, plants need then yes they will absorb ammonia. However looking at your pictures the plant appears to be a Anacharis and it doesn't look well. If all nutrients were available it should have grown enough to fill the entire aquarium in 5 months you have had it. Those facts tell me it is not growing well and as a result it might not be absorbing any significant nitrogen (ammonia, nitrite, and nitrate) from the water . Even in a well planted aquarium with fast growing plants it is possible to get significant ammonia levels.

Get a test kit, In a properly cycled tank with healthy fish added you should have not lost any fish in a 5 month period. The frantic activity of the fish could be a indication of a serious water quality issue.

 

[BOBJOESIM]

If your water has all the nutrients, especially micro nutrients, plants need then yes they will absorb ammonia. However looking at your pictures the plant appears to be a Anacharis and it doesn't look well. If all nutrients were available it should have grown enough to fill the entire aquarium in 5 months you have had it. Those facts tell me it is not growing well and as a result it might not be absorbing any significant nitrogen (ammonia, nitrite, and nitrate) from the water . Even in a well planted aquarium with fast growing plants it is possible to get significant ammonia levels.

Get a test kit, In a properly cycled tank with healthy fish added you should have not lost any fish in a 5 month period. The frantic activity of the fish could be a indication of a serious water quality issue.

Well no, I have a testing kit that's why I'm confident ammonia is at zero, however I haven't gotten around to getting one for nitrates because my lfs didn't have it for that. Also I have amazon swords in there as well, the anarachis I trim because it grows all the way to the top and it gets ugly when the top floats along the surface...
Edit: I also cycled my tank for 5 weeks with a canister filter rated for 60 gallon tanks (this is a 30 gallon one) before I got the fish. I'm not entirely sure what's going on...

 

[BOBJOESIM]

Well she has what seems to be a cyst on her left side and the bottom is a lot brighter colored.
Again, I've done two water changes in the last two days (30% each) to make sure that ammonia is at zero, used the test kit as well.
Anyone have any ideas what it could be? I don't want to lose the rest of my fish.

Edit: To answer previous questions: My pH is on a rather high side (really close to 8 because of the tap here), alkalinity I'm not sure, alongside nitrates and nitrites as I couldn't find test kits for those...
I do use a vacuum filter (the one that looks like a suction cup with a hose), every week as that's how I also do my water changes (15%). The food itself I've gotten a bit liberal with giving as I now have fry and I'm testing how much they need to eat...However I'm pretty sure that's not a part of the problem.
I'm now thinking maybe it's a fungus of some sort?
Edit 2: Although the one recent thing that stands out for me is the recent changes in temperature in the aquarium (New York has gotten extremely cold again), my heater isn't entirely reliable so the temperature fluctuates between 76 to 82 degrees.

 

[BOBJOESIM]

Update, a month later and she's somehow still alive, yet the only adult I have left. So bizarre, as now I have around 13 fry to take care of.

 

[NickAu]

temperature fluctuates between 76 to 82 degrees.

Thats a big swing, maybe you need a new heater or 2.

I have around 13 fry to take care of.

Soon you will have more..... Lots more.

Platies can have 50+ fry every 30 days and they can start reproducing at 6 to 8 weeks old.