hi and thanks as this is my first post...HELP please! My neon tetras are dying fast in the past 2 weeks after buying 6 new ones from Petco. I had 4 in there already and wanted to get more for them to swim together in. Also have 3 catfish (1 died) and 2 glow fish. My 30 gallon tank has been up and running fine for 2 yrs. Always bought my fish at a pvt fish store until he went out of business and i had no choice but to go to Petco. No major probs at all other then usual loss of a few fish over that period of time. Otherwise all have been great! So i went and bought 6 tetras (already had 4 tetras in tank doing fine for months) and I came home acclimated correctly as always and now after 2 weeks ALL are dead except for 1 left today!!!! I never had any probs w my tank until i brought these fish home. I also lost 1 catfish in this time and till then i had 4 that were solid as could be in there until these new tetras. My readings are PH 7.6..yes i know thats not ideal but its in the range and my tank has been established w no such rapid dying in over 2 years...I do reg changes n cleanings to the letter! My ammonia is normal too...The only thing I add which ive had no probs w is salt after each cleaning water change (yes i put in proper amount..only what i take out!)..... Bottom line is I am pretty positive its the fish i got from Petco...and its strange it affected only th e other Tetras i had in there (besides the one catfish) as well. I had a total of 10 tetras and after 2 weeks i have now ONE............I could see MAYBE the 6 from petco dying but why then my other tetras that were fine before then? disease??? bad fish? diseased? They had no spots o nthem or anything..one day normal and next day dead...My water temp is steady at 75...not over feeding.....The only other thing I Hve done differently is use a new vacuum...its stronger then the last one i had (w the lil bag on it battery operated)...did it suck too much when cleaning and open up a plume of something????????? I went to my other fish store i found and the guy was terrible. He tested my water and again i knew the readings and although not perfect 7.0 the previous fish were fine in it all these months ...UNTIL i put in the Petco fish....so i knew he would simply saying my PH was high and he sold me the ph buffers (not ph down but the buffers instead)....I DONT THINK ITS THE PH....again it was that reading 2 years ago exactly..and i know a stable ph is better then a fluxing one.....Should i stop trying to bring it down in fear of the change killin my other fish? Each day they are dying and im down to one...I have done a 40% change 2 days ago and after todays death i did a 10% change..... PLEASE HELP!!!!!!!!!!!!!!!!!! Should i try 6 more tetras from a new store or?????????????