Dead Guppy today 1 month after a dead Dwarf Gourami

[Omi]

So this is a relatively new tank that was set up in March 4th-ish.

There were 3 black skirt tetras, 2 sunburst platys, 2 mollies, 4 guppies, and 1 Dwarf Gourami to start off in a 70g tank.

In the first week of April, the dwarf gourami died. I wasnt sure if it was because he was alone or was something else like a disease, but it didnt seem to affect anything else at all.

Today, a bit more than a month later after the Dwarf Gourami died, one of the guppies was found dead lying on the ground where he usually slept. I was told by someone that the same Guppy seemed a bit sick and was flailing around on the ground just a day before.

I'm not sure if this is a disease, if it's bad water quality as I've been regularly changing it biweekly, if the death of the 2 fish are related or it's simply the fish itself as it was purchased in the big branded Petsmart.

If someone could help me diagnose this situation and can help, I'd gladly appreciate it.

Thanks

 

[DwarfCichlidLvr]

What are your parameters?
This can be expected.
Im sure you aren't doing anything wrong. If you're afaid of buyinh fish at a big box store them look around to see if you have an LFS near by.

 

[Colin_T]

What is the ammonia, nitrite, nitrate and pH?
Pictures of the fish?
What symptoms did the fish have?

 

[Omi]

What are your parameters?
This can be expected.
Im sure you aren't doing anything wrong. If you're afaid of buyinh fish at a big box store them look around to see if you have an LFS near by.

Ph is at 6.3
Ammonia at 0.25 ppm
Temperature at 77 F

is what I can gather at the moment.

I'm not sure if this has any relation but within the last week, the black skirt tetras have been pretty aggressive mostly to each other but I did catch slight aggression from one to other fish.

 

[Colin_T]

The pH is a bit low for guppies who prefer it above 7.0.

You want the ammonia and nitrite levels on 0ppm at all times. A slight ammonia reading could make the fish sick and the low pH would too. Then the fish just died because of the stress.

Do a 75% water change and gravel clean the substrate every day until the ammonia and nitrite levels are 0 and the nitrate is less than 20ppm.

post pictures when you can.