Post Mortem Not Emergency (advice Leading To Prevention)

[mangoed]

Hi,

Yesterday, I noticed that one of my threadfin rainbowfish had red, inflamed gills. It was at the surface of the water trying to extract oxygen from the air. I performed a 20% water change and had intended to seek advice from the LFS today but, unfortunately, the fish died during the night.

The chemical properties of the water in the tank before the water change were:

pH: 8
ammonia: 0
nitrite: 0
nitrate: 5-10
kH: 110
gH: 220
temp: 26.8C (80.25F)

The size of the tank is 100L (26.5 US gallons). The current inhabitants are 2 x Corydoras reticulatus, 4 x "lambchop" rasbora, 2 x red/rummy-nosed tetra (difficult to determine exact species), 2 x threadfine rainbowfish, 3 x Ottocinclus, 2 x marbled hatchetfish. These are very small fish - currently no more than 50cm total length in the tank.

When I tested, the pH was much higher than I would like, the water change took it down to 7.7 and I had intended to keep changing until it returned to that of my tap water (about 7). However, in the hours since the water change, the pH has begun rising back towards 8 again!

I guess that I have two questions:

1) Any idea what was wrong with the fish, especially so that I can try to prevent it happening to any of the others?
2) What would cause the pH to rise to this level and what can I do about it?

Thanks.

-dan

 

[Imber]

I can't really help you with what happened to the fish, but I can help on the ph issue. My ph out of the tap is 7.8, but it settles to 8.6 in the tank! I've read that this is because when it comes out of the tap it isn't aerated and as your filter turns it in the tank it becomes oxygenated and therefore the ph rises. When I realized this was happening, I started aging my water a day or two in a plastic tub with an airstone in order to get that ph up to match the tank.

 

[jollysue]

It is hard at this point to say what may have been wrong with the rainbow.

But as to the PH: What do you have in the tank> Any shells or substrate with shells? Anything with calcium. Ph will change in a tank, but from 7 to 8 is a pretty large increase. So it will do to inspect what is in the tank for what might be causing it.

 

[mangoed]

It is hard at this point to say what may have been wrong with the rainbow.

But as to the PH: What do you have in the tank> Any shells or substrate with shells? Anything with calcium. Ph will change in a tank, but from 7 to 8 is a pretty large increase. So it will do to inspect what is in the tank for what might be causing it.

Hi,

I basically have a three-layer substrate. Gravel, over Eco-Complete, over sand. There are a couple of bits of mopani wood, some slate and a lot of plants. It has seemed stable for some months now (though, I admit, I haven't closely monitored pH, more ammonia/nitrite). The rainbowfish had been in the tank for about five weeks and had previously seemed "fine".

-dan

 

[jollysue]

This may help understand what is going on:

ph adjustments in the tank

water changes and ph