Unwell fish

[black ghost]

I wouldn’t put it back with the others.

[black ghost]

He looks quite old from the picture. Maybe he's been whacked near the swim bladder at some stage.
Males will harass each other when there's no females (and often when there are).
If the hardness is 7dGH (that's what I took it to be) then it's at the extreme end for guppies.
Guppies aren't usually bothered by nitrate values. They've been successfully kept in lab conditions up to 1000ppm.
(Ref: https://www.waterboards.ca.gov/water_is ... ef2426.pdf )

Seems you’ve linked the wrong paper Ian. That one says this about guppies…

“Rubin and Elmaraghy (1977), after examining the acute toxicity of KNO3 to guppy (Poecilia reticulatus) fry, calculated 24, 48, 72 and 96 h LC50 values of 267, 219, 199 and 191 mg NO3-N/l (Table 3).”

(Table 3 has the same info in table form).

The info means that different batches of guppies were kept at 267, 229, 199, and 191ppm of nitrate. The corresponding LC50 numbers mean that those times (24hrs, 48hrs, 72hrs and 96hrs) were how long it took for 50% of the guppies to die.

So… the paper shows that nitrate levels of 191ppm will kill 50% of guppies within 96 hours. At 267ppm half will die within a day.

There’s no mention of guppies at 1000ppm, which would obviously kill them very quickly.

(Nitrate makes haemoglobin incapable of carrying oxygen. It does this at all concentrations, so any level has an effect.)

[black ghost]

Actually they weren’t kept at those exact levels. They were kept at various levels and the LC50 levels for 1,2,3 and 4 days (which are standards) were calculated from the results.

LC50 is the time it takes for 50% of the sample to die. Like a half-life, in effect.

[plankton]

That'll be the senility kicking in then.....
Or maybe it had just gone into my brain as a muddled confusion. I can no longer find the paper I thought I'd read.....
Anyways, I wouldn't keep any fish above 20ppm if I could help it, and certainly not above 40ppm.

[fraserh]

A wee update on my Guppy.

I decided, against advice, to return him to the aquarium as I couldn't sustain what I had in place with the jar, changing water twice a day etc.

That was on Thursday and initially things didn't look great but since then he's made a marked improvement.
He's no longer swimming on his side or upside down and has become more active each day. He still wildly spins round occasionally but is eating well and hopefully will continue to improve.