Help Stressed Pregnant Gubby?

Question
Hello,
I purchased a female pregnant gubby yesterday and also to company my other fish which i do not know the name of but it is slightly bigger than her and is yellow and both go well together with no problems, So the day i purchased her i kept her in her plastic bag floating over the tank for 15 minutes like usual then let her in with no problems, then i did some research on them that day and found out that you should seperate the pregnant gubbys or else the other fish will eat them so i did seperate her (caught her in a net and took some water from her tank and filled it up in a small one) and left her in their for a day and when ever she saw me she would go nuts and swim around the small tank like crazy! So i just ignored it and left her didnt fed her that day either as she didnt want any food when i did, and the next day i found that over night my yellow fish died in his seperate tank :( i dont know why guessing stress, so i took him out and kept 30% of the water in a jug and the rest threw out and cleaned the pebbles with hot water only and then re filled the tank with fresh cold water and the left over 30% of the old water and added some salt starter a table spoon in the tank provided from pet store and put the pregnant gubby back in that bigger tank since no one was in there now and as soon as i put her in she swam around very quickly checking everything out then went down to the bottom sitting on her stomach and breatheing fastly at first probly from all that swimming and now shes auctally slowed down and whenever i come in and go close up to her she auctally stops breathing for 5 sec then goes on again i also noticed that on top of her stomach on her left side it is a shiny white/silver like it has faded away and after checking on her 15 minutes later (now) that faded colour has gone and its back to her normal colour as i purchased her with but her cheecks are a shiny faded silver colour still and shes not moving shes just sitting at the bottom corner?

Answer
Kassie,

I am not sure what the question is but I am assuming you are talking about a guppy. When you changed out the tank, you started the filter cycle all over again. It is never a good idea to do this if you have fish in the tank. Now, you will have to check your ammonia and nitrite levels daily to make sure they are at zero all the time. If she is pregnant and is hanging out at the bottom, she could be getting ready to have the fry. Make sure there are a lot of plants in the tank so that the fry have hiding places. The female guppy will eat the fry if she gets a chance so it is a good idea to remove her from the tank as soon as she is done. There is no need for salt in the tank since guppies are fresh water fish. I ONLY use salt when treating a fish with an illness or injury.