Re: [RML] Melanotaenia trifasciata

Bruce Hansen (bruceh at
Sat, 14 Aug 1999 17:33:35 +1000


I can only quote from my experiences which are not accompanied by continuous
or comprehensive water parameter testing and Goyders seem to get less things
wrong with them and live longer when kept in harder and more alkaline water
(as do most of the PNG lacustrine rainbows as well as those from the bigger

I agree with the statement about wrong pH reducing egglaying - I'm sure it
can be too acid as well as too alkaline, for each species. So reducing
either by dilution with water changes would approximate rain and often
stimulate spawning. I remember when Adrian dawson was having trouble getting
his Gap Creek Tris to produce eggs and Ray Leggett suggested the addition of
Epsom's salts which had worked for him before on problem fish. BTW it did

I'm not sure if it works by raising pH, hardness, TDS, or all or none of the
preceeding - or perhaps the fish give in and spawn to stop Adrian from
adding even more epsom's salts and give them even worse diarrhoea:-)

----- Original Message -----
From: <peter.unmack at ASU.Edu>
To: <rainbowfish at>
Sent: Saturday, 14 August 1999 10:42
Subject: Re: [RML] Melanotaenia trifasciata

> You're right, I don't have the physiochemical data, although I'm sure we
> both find data to back up our ideas. My main point was that many people
> into the trap with Australian fishes of paying too much attention to
> their fish are at 20 or 200ppm. For _most_ of them it doesn't make any
> difference at all.
> Does anyone have any accurate data on the lower pH
> limits that rainbowfish will successfully spawn and develop at? I
> know folks who have had rainbows not reproducing, checked their pH, found
> acidic, raised it and gotten eggs shortly after. Unfortunately few people
> keep good enough records to really know for sure.
PS. I wonder if they might have been PNG rainbows that usually like it
around 7.5 - 8 Peter


Bruce Hansen, A.N.G.F.A., Advancing Australian Aquatics.

Bruce Hansen, ANGFA, caring for our aquatic ecosystems.

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