Fish in danger! :(

Question
QUESTION: So I got an aquarium in november and I initially started with 6 fish (3 glofish, 2 guppies, and 1 glass cat). I was told that you can mix the glofish with the other tropical fish. One day, one of the guppies died on the gravel near the fake plants. After awhile, we decided to buy 2 more fish (1 pregnant platty, 1 platty) from another store. This person told us we couldnt mix glofish with others because theyre too aggresive? Then, we bought a female guppy and another glass cat in about a week. After a week or two, the older guppy died. Today, the pregnant platty died. All three fish died in the same spot, but the platty died upright whereas the guppies died upside down. What happened? My family is suspecting that the glofish are snacking on the other fish and are too aggressive. I have no clue what to believe...help please? (Thanks for taking your time to read this insanely long question!)

ANSWER: Michelle, your question is not long, and wither way, I am here to help. First about the glofish, they are a genetically modified form of a zebra danio. They are injected with Bioluminescence which gives them the glowing effect. I have never seen or heard of wither one of these fish being aggressive. I don't know who you talked to, but they obviously have no idea about community aquarium fish. They are a perfect community fish, they are peaceful!? The only negative thing about these fish is that if you mix them with fish that are easily stressed out by fast moving fish such as these glofish, it can be fatal. For best care, keep this peaceful fish in small schools with equally non-aggressive fish in your tank.  As far as the glass catfish, they should be kept in groups of five or more to stay healthy and happy. If they are not kept in groups, they will often go into a state of stress, stop eating, and waste away. The Ghost Glass Cat does not like a lot of light and in brightly illuminated aquariums, it will usually hide from the light. However, they will come into the open and swim around in darkness or low light conditions. Ghost Glass Cats should be kept in aquariums with plenty of rocky coves and hiding places. The platy that you may have though was pregnant, could have been suffering from an internal bacterial infection which caused it to become bloated? Who knows. It didn't make it so......... As far as the guppies, They too are a hardy fish, great for beginner hobbyist. All of these fish species do best in small schools, 3+. Being that there has been fatalities in the tank with all of these fish, I would hope and encourage you if you haven't already, check, test and correct and problems with the water quality in the aquarium. I use quick dip test strips which give you results on 6 different parts of water quality. Work great. Try this and see if there is anything that needs to be corrected according to the test strip results. Once you have done this, try again with the fish if you wish, but in larger schools as I have mentioned. Good luck, I hope this helps, and I apologize for the delayed response. Feel free to contact me in the future if you need any further help.

---------- FOLLOW-UP ----------

QUESTION: Thank you soooo much!!! I have learnt that the glass cat fish are better off in 5+,and that was the reason why i bought another one to accompany the first one. The second one i bought was so much more energetic and not shy at all. It likes to move around in the open whereas the first one stays hidden my the filter. I do have alot of plants for them, but no decor yet! I researched a lot over the past few days and eventually discovered some problems... (no need to apologize for the delay, it helped!) 1. The pregnant guppy turned darker, not just the area where its pregnant but the full body. She started to breathe heavily through her mouth and I'm suspecting gill fluke or something?? And that was how the pregnant platty died, i think (she was always up at the surface and breathed through her mouth the day before she died). 2. The other platty seems normal, but I'm not sure if her gills were red before or if she is also infected. the glofish and glass cats are all fine, and i hope the parasites from the gill fluke thing doesn't get to them.

I took a walk to my local aquarium store today and bought many things: water tester, gravel vaccuum, some kind of ick medicine (i'm suspecting the fish also have ick becuase of some white spots but they're only a few tiny spots), and aquarium salt. I haven't done a water change yet, but today i tried cleaning the gravel and it didn't work really well (the crap didn't get sucked into the tube and made the water dirty) and scared the fish alot. I heard that you should scare the fish or else they will die? Anyways, I took some advice from the fish store and added 1 Tbs of aqurium salt for every 5 gallons and added a few drops of the ick medicine (they adviced half the dose because guppies are sensitive)
AND i also took the water tester and i think i may have found the problem.
The results were:
Nitrate- 80 ppm
Nitrite- the pink was darker than what was on charts (yikes!!)
hardness- 150 ppm
chlorine- 0 ppm
alkalinity-80 ppm
pH-7.2 ppm

I might have been feeding them too much and they poop too much..well after all that i've done, what else should i do? i think i'll do a 25% water change soon and maybe I should buy live plants? How do I keep my nitrate and nitrite levels down? I was also told to not do a water change because its a new aquarium and it will put a lot of stress on the fish. Thanks a bunch!!!!! Do you need an pic of my fish to help figure the disease?

Answer
Well. I don't know why they would tell you to not change water. That's the main thing to do to lower the nitrite and nitrate levels. You must do this!!!!!!  The nitrite are the most fatal so be sure to do water changes until it is at a safe reading. That is probably the main reason why the deaths occurred. It sounds like you have a good understanding of what you need to do now. If u need any other help let me know. Just be sure to do water changes daily until the levels are normal.