Guppies Dying - PH Problem? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 2 Old 05-22-2010, 12:05 PM Thread Starter
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Guppies Dying - PH Problem?

I have a 90 litre tank. When I got the tank for a present, I followed all the advice on this forum about fishless cycling and managed to get everything set up correctly regarding nitrates, amonia, nitrites etc etc.

After checking everything was ok, I went to get some fish to get me started. I got 5 guppies and a swordtail. Initially, they did really well. However, after a couple of weeks, the guppies started getting fin rot and then died a feew days later. Treatments didn't seem to help at all.

5 weeks on, I now only have the swordtail and one guppy left. Both seem to be ok with no sign of fin rot.

My amionia, nitrate, and nitrite levels all remain ok. However, I live in a soft water area and my PH varies between 6.4 and 6.8.

Stupidly, despite following the advice regarding the fishless cycle etc, I seem to have totally ignored water hardness and PH levels when stocking.

I have two questions:

1. Is the PH level the likely reason for the guppy deaths?

2. With my PH levels as they are, can anyone offer advice on more suitable species for a 90 litre tank (I want a community tank).

Many thanks.
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post #2 of 2 Old 05-22-2010, 02:23 PM
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"Fin rot" could have been something other than true fin rot. I won't speculate on that, although it is a possibility that what you observed was the fish's natural reaction to acidic water. When the pH and hardness are significantly below the fish's preference or tolerance level, white mucus can occur on the fish; I've no idea whether this occurs on fins or just the body. As I said, this is just an observation and not a diagnosis.

But I do have some advice on the fish and water parameters, your second question. Livebearers will not be happy in soft acidic water. They occur in waters that are moderately hard with a basic pH (between 7 and 8 generally). As most available will have been raised in similar water, trying to adapt them to soft acidic water is not something I would recommend; these fish in particular require mineral content in their water or they can develop internal issues. Where I live we also have very soft (near zero GH and KH) water and everyone here has no luck with livebearers unless they harden the aquarium water with calcareous material like dolomite, crushed coral, marble chips to provide some mineral that will raise the hardness and correspondingly the pH.

Your water is ideal for the majority of aquarium fish, which means almost everything from South America, SE Asia and West Central Africa. There are a few exceptions, but generally the fish from these areas prefer soft acidic water. There are characins (tetras, hatchetfish, pencilfish), rasbora, smaller danios (thinking of your aquarium being 90 litres or 23 US gallons), anabantids (gourami, betta) small loaches and catfish, dwarf cichlids...quite an array. And many of these are small enough to form a nice display in your size of aquarium. Most of these are shoaling fish that need to be in small groups. You can check the info in the fish profiles on this forum for lots of info on water requirements, behaviours, compatibility, etc. of each species.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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