Please help! Fin rot

[Curri]

Hi I am new to the forum, I have a 29g tank that has been fully cycled for about 4 months. I have sand but no live plants. I have 5 guppys and 5 bronze corys. About a week and a half ago I noticed one of my corys looked like it had the early signs of fin rot. I checked the nitrates with the test kit (not strips) and the ammonia with strips-Nitrates 5-10, and the ammonia was ideal/safe (it is hard to differentiate between the colors). I immediately changed the water (25%) and treated the tank with melafix for the full 7 days then another 25% water change. After the 7 days the cory was still alive but without a tail, and I noticed signs of fin rot on one other cory. I have been doing daily water changes for the past 3 days. Today I found a guppy dead, When I scooped it out of the tank I saw a little fin rot, but it was barely noticable if it was even there at all.

What should I do next? I was reluctant to treat the tank with antibiotics etc because I have heard it can cause problems of its own but obviously I need to do something

Could this problem be from over feeding the corys? I was crushing up 3-4 shrimp pellets every morning for them, they can never eat it all within 3-4 minutes but my nitrates never spiked so I assumed it was fine. Can corys get stressed/sick from over eating? I always thought the decaying food will impact the water quality which will impact the fish. But can the fish simply over eating cause issues?

I have cut way back on the feedings and I am looking into treating the tank with maracyn.

I would really appreciate any suggestions!
Thanks

 

[JuiceBox52]

What are your ammonia, nitrate and nitrite levels? How often do you do water changes and how much water do you change at a time?

Do a 75% water change daily for two weeks and make sure you dechlorinate your water before adding it to the tank

 

[JuiceBox52]

Do any of them seem to be picking on each other?

 

[Curri]

Do any of them seem to be picking on each other?

none of the fish are picking on each other, the guppy’s chase each other around a bit but nothing excessive or different from before. The nitrates are 5-10 and ammonia Strips I use don’t give a # it’s just marked as “Ideal” or maybe “safe”(it’s hard to tell The difference between the colors) I use a test kit for nitrates tho not the strips.
I will do a 75% water change tomorrow, I’ve been doing 25% every other day.

 

[Colin_T]

Pictures?

Can corys get stressed/sick from over eating? I always thought the decaying food will impact the water quality which will impact the fish. But can the fish simply over eating cause issues?

No, fish can't get sick from over eating, but uneaten food will rot and can cause water quality problems and encourage protozoan and bacterial infections.

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As Juicebox said, do a 75% water change and gravel clean the substrate every day for a couple of weeks.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Post pictures of the fish.