Swordtails dying

[kevcol]

I’ve had three (of 10) swordtails die off in a community tank over the last week or so.

Water params are decent, per my API tests:

ammonia - 0

nitrites - 0

nitrate - 20

ph - 7.6

high-range Ph - 7.4

It’s a 75 gallon, with FX4 canister filter (which is rated for bigger tanks.)

Temp: 78-80

I got 10 about a month ago. They were in with one Angelfish, four glo tetras, six corey cats and one bristlenose plecos, so understocked.

I noticed some swordtails hiding in plants, others on bottom of tank. One died, and I suspected the angelfish of bullying, so moved it out.  They still seemed to be hiding, then another died. Now the glo tetras can get nippy, too, so I moved them to another tank. Today, with  just the swordtails and corey, I found another dead one.

Of my survivors, four at the top of the tank (no longer hiding in corners), but three are just sitting on the bottom, kind of hiding. Since the others died, I’m assuming this might be illness (rather than birthing fry.)

No other species have died or shown any illness, lethargy.

Any idea what’s wrong? Or how I can figure out? 
 

[kevcol]

BTW, I mostly feed Tetra-brand flakes and crisps

[Henry the fish keeper]

Are there bodies skinny...? Do they have white stringy poop?

[kevcol]

No

[Henry the fish keeper]

Ok, then I have no clue what is causing your swordtails death. Maybe @Fish Folk or @Colu knows.

[Colu]

What your kH and GH and have you noticed any rapid breathing and are they eating ok did you Qarantine them before adding to your tank @kevcol

[kevcol]

Unfortunately, I don’t know the kH or GH. I’ll have to learn how to test for that.
 

My tap water had very low pH so I added crushed coral to the filter, which helped pH. I’m not sure if that affects kH, GH.

Breathing and eating seemed fine up until recently. Now the ones on the bottom are pretty sluggish, so not eating much. The others seem normal.

Oh, and no, I didn’t quarantine. Though they were fine for a few weeks. (I’ve had them close to two months, and had no problems before the last week or so.)

[Colu]

With out noing your kH and GH it's difficult to tell as low kH and GH can cause health problems in livebearers due to lack of minerals  aquarium co-op test strips test for GH and kH or your can get API kH GH test kit

[kevcol]

I’ll pick up some tests. Thanks