Sudden deaths..?

I have 65Liter plastic contrainer temporarily as aquarium with equipment for 100Liter aquarium. Yesterday I did water change. I use , very famous water conditioner here and reliable.


I had 6 male guppies,
3 tetras,
4 small cory catfish.

Now 2tetras, 1guppy and 1 cory catfish died for unknown reason. Yesterday with water change put slightly (less than 1*c) if the cory catfish would be ready to breed, I don't think it affect the tank much at all thought.


Parameters are good, ammonia and nitrite are 0, Nitrate is 10ppm (probably cus they died at night and after school day I check them).
I don't know how to read PH as, if it is higher than 7.4 or lower, because it is brown-ish. Normally PH is about between 7.4 and 7.8. Meaning it has crashed now?

 

Did you test using the high range or regular pH test? I would try testing with the one you didn't use so you can be sure of what your pH is now. What was it before? Can you test your tap water to be sure nothing changed there? How much water did you change?

 

Tested using high range PH tester, because the API saltwater master test kit doesn't come with the regular PH test and it is super super hard to get freshwater kit here.
Before my waterchange my parameters were 7.5PH, 0ammonia, 0nitrite and 20-30nitrate.

My tap water has PH is just slighly off the chart, tiny bit coloration towards brown-ish, I'd estimate not below 7PH, and between 10 and 20ppm nitrate.

At water change I did between 40% and 25%

 

Geez, I didn't even notice that the card read saltwater! If it's only dropped 0.2 or so that shouldn't have caused the deaths.

What was that you were saying about a temperature difference?

 

Because cory catfish breed after rainfall (temperature loss around 2degrees or so) I test the water by hand if it match the aquarium temperature and if it was slighly colder, I wouldn't mind, just so if the cories would breed. I don't think this is neither nothing significant.

And also I a DIY media filter? Idk, but it supposed to boost beneficial bacteria, I clean carefully a coca-cola bottle and cut few holes on bottle cap and bottom of the bottle, fill with media and put air pump thru bottle cap and bottlecap to bottom of the tank.

 

You don't have a thermometer? I have trouble getting an accurate idea of temperature by feel.

 

I have like stick thermosmeter atm at the hospital tank, and it shows 22*c (24-25*c in room), at summer it is about 28*c(+30*c in room). I should buy better and multiple.

But for this big tank I just fill 2L clean bottle with water, go to my aquarium and test the aquarium water by finger, and then the bottle, gives estimate temperature, then I add them to 4L bowl and put conditioner, mix well and put in the tank.

Now as I think about it, the temperature is a little bit low for tropical fish.

Oh resolved, these fishes are new that I bought (the ones that died....), I bet the reason why they die, is that I took their earlier living conditions accidentally as granted and they have been used to warm temperatures, now sudden change in temperature and continuing "freezing" water for them made them to die eventually. I guess I learned my lesson...

 

That's probably it. Definitely get a thermometer when you can!