New fish dying

[Newbie3141]

Hey guys, I m back....this is regardin my old posts.... Today I got my aquarium water test kit delivered to me...It took a long time bc I had to order it from a place far away from my state cuz we dont have those test kits available out here....
My water parameters are as follows
pH-7.8
Ammonia-0
Nitrite-0.25
Nitrate-10
Temp.-30-31C
As many of you guys know...almost like 60-70% of the new fish I get die within like 2-3 days with no sign of disease...So what could it be?
My barbs r doin fine the one with white spots....still has the white spots....they seem permament...idk y they suddenly appeared one day....one out of 2 of my male guppies also died today....he was doin completely fine till yesterday night...no sign of disease or stress.....
I would appreciate everyone helpin and lettin me know some of the probable problems I m havin with the tank and solutions...
I am kinda new to these testing n stuff so I will update the readins if they come out different tomorrow...
P.S. I have got no more fish since the last time ( when I got 4 female guppies n they all died within a day)
These are my previous posts (in case you forgot me)-

Help!! I hv got a guppy problem

hello guys, Ummm.....so I hv got a female guppy problem..... So, here's a lil timeline of wht happened....I bought 4 female guppies frm the store on the sunday mornin....as soon as I got home one of em inside the bag wasn't movin...she was breathin tho....I acclimated em n put em inside my...

www.fishforums.net

I urgently need help with ich

Hey guys, I think one of my fish is suffering from ich but I m not sure about it. Can somebody please help me diagnose the problem? Only one outta the 5 rosy barb has tiny white spots on jus the fins( dorsal,tail, swim fins,all the fins). Each fin has around 7-10 white spots. He is eating fine...

www.fishforums.net

Thank you very much to everybody taking out time for me....

 

[Sgooosh]

what stores are you buying them from? some stores buy from places that have drastically different water conditions and antibiotics. and guppies being the delicate fish they are are very sensitive. basically they have no immune to the common things in your tank.

The nitrite is also too high. It should be at 0

edit: you can lower nitrite by water changes and just waiting for tank to cycle

 

[Newbie3141]

Edit I checked my nitrite today and it came out to b 0 2 times in a row...so wht cud b the problem?
Temp.?, overstockin?.., disease?,stress?, or bad conditions provided by the sellers?....

 

[Sgooosh]

Edit I checked my nitrite today and it came out to b 0 2 times in a row...so wht cud b the problem?
Temp.?, overstockin?.., disease?,stress?, or bad conditions provided by the sellers?....

how long has your tank been set up?
perhaps it is not cycled yet
or it is overstcking

It is not caused by disease or stress or sellers