Nitrate levels.

[Ruthless]

Over a month ago I bought 3 ADF's. 2 boys and 1 girl. They share a 5 gallon tank. It has a light filter, gravel bottom, and plenty of hiding. The female frog from day 1 floated around the top more, ate less then the boys, and also her stomach was slightly puffier then the boys but not like the ones that suffer from bloat. I did notice one side was a bit bigger then the other. I just figured maybe she was full/constipated. Even though she floated around way more she was also more visible then the boys. Hiding less and swimming around.
Either way 2 days ago I get home from work and I was looking at the frogs like I always do when the girl suddenly flipped over on her back and started almost like convulsing. I do not really know how to explain it other then like when a dog is on their back and trying to scratch it off the carpet. I waited maybe 1-2 mins just watching her in panic because I just knew something was not right. I ended up moving her to a big bowl to keep a eye on her and hope the boys did not get infected with something if she is sick. Either way a hour later she ended up dying. She could not stay on her stomach even though at times she would fight to flip over. I would help her with the net and seconds later she would be back on her back. I even helped bring her up for air.
While this was going on I left her with my bf for maybe 20 mins so I could go get my water tested and ask advice.
Everything with my tank was perfect except my nitrates were high. So I instantly went home did a about a 30% water change, cleaned the gravel, plants, and house. I then put my boys back in.
I have the at home testing kit and I just did it today. It says the following
GH- 60 KH- 40 PH- 7.0 No2- 3 No3- 40

I do not understand the No2 and No3. Also Im wondering if I should change the water again. If my girl died from nitrate levels while the boys appear to be healthy.. Im just lost.

[spotfin]

Perhaps your filter isn't big enough. the NO2 reading is way too high, it should be zero. I'm guessing the numbers are in ppm or mg/l.

[Mentat]

Ammonia (very toxic), Nitrites (less toxic), and Nitrates (not toxic unless concentration is high, keep below 25 PPM) are read in Parts Per Million. What kind of test are you using? If paper strips they just serve as warning and are inaccurate. Presence of Nitrites (and possibly Ammonia) indicate either no filter or an uncycled one.

If no filter, suggest 25% water change daily and do not overfeed. If you have a cycled filter; 25% a week should work. Beneficial bacteria will also live on substrate; but if you cleaned that in tap water, they all died. Gravel is an impaction risk if ingested. Suggest either bare bottom or very fine sugar sized sand.

If you have a filter, the media should be cleaned during weekly water change with tank water you are removing. When replacing media some of old one must be left in filter (i.e. don't replace filter pad/foam at same time as other bio-media in filter). Good luck !