Last Sunday I added two new WCMM to my tank. Over the past week i have now lost 3 fish, all with the same symptoms.

The fish are all OK in the evening, however the next morning each fish has it's mouth open, almost as if it's jaw is fixed in an open. The fish has now physical signs of anything else wrong with it. Over the day the fish will seem to lose control of it's swim bladder, swimming upside down, rolling over and over and ending up either in plants or lay on the tank bottom. They always seem to finally go two hours after the second feeding of the day.

The fish this has happened to is two WCMM and one Zebra Danio.

Tank:

size:130L
Substrate: 50-50 mix of pea gravel and sand.
Setup: 3 years
plants: 6 cabomba, 3 plants got from P@H several years ago that I've never been able to identify , 5 Lindernia rotundifolia and large amount of elodea densa

Current fish: 4 WCMM, 4 Danios, 4 platty. several pond snails.

Water:

Temp: 22C
PH: 6.5
Ammonia: current 0.25 although usually 0.
NO2: 0
NO3: 25

* The fish has no physical signs of anything else wrong with it.

Is it the new fish or the established fish that are dying?

Do you have an airstone running in the tank? Am wondering if CO2 from the plants at night is affecting them.

You have ammonia which is slightly concerning, but given the low pH it shouldn't be causing a problem as at that pH it will almost all be NH4+ which is far less toxic.

Your pH is perhaps on the low side for the stock you have; what is the gH? If it's the established fish that are suffering (the Danio obviously is) then at three years, if the water is a little too soft and acidic they may just be dying coincidentally from a combination of old-age and lack of minerals in the water.

Hi Graham.

First of all pH 6.5 is too low for platy. It's best to increase it to 7.5 so it'll suit all of the inhabitants :D

Ammonia raise is because of the dead fish so don't worry much.

It's probably that your new WCMM has some kind of sickness in them already and when you introduced them to the tank, the bacteria transfered to your healthy fish. That's why people usually have a quarantine tank and keep the fish in there for about a week to make sure the new fish are disease-free.

Keep a close look on your fish and see for any other sympton. Any fish appear to be unhealthy should be move out immediately. Also set up a quarantine tank and raise pH to 7.5 gradualy.

Quarantine tank doesn't have to be a fish tank. You can use food safe box or anything water tight and and a filter,heater running in it

Thanks,

I'm not to worried about the ammonia as introducing new fish seems to show a small peak for a few days.

I did have a Quarantine tank, unfortunately my 4 year old got to it with glitter so decided it was safer not to use it. I'm in the process of using Bicard to increase the Ph but it slow as the tap water is around 6 or thats as low as my testers went last time I measured it.

So I assume that the 2 WCMMs died are the new ones?

You should do something to make the quarantine tank usable again.

Before increasing your pH, it's better to test for your water hardness first. Increasing kH only will not guarantee stable pH.

What kind of test do you use?

Sorry Nathan you're wrong there; it is kh that stabilises pH. gH plays no part in buffering and alkalinity. gH is important in its own right and it is gH we mean when referring to the ideal hardness level for a species, but kH is the one that governs pH stability.

Opps, thanks FL.

But isn't gH drop over time?

The WCMM that were effected were one original and one new. The other new still seems fine.

Unfortunately it looks like one of the platys has started to develop the same issue.

I'm thinking about a dose of salt.


Luckily I work at universities Bio Labs so I can get simple tests done, I also have King British Test strips at home.

Quote:

No gH does not fall over time. In fact it can even rise if water is topped up rather than being changed as it should be.

kH falls over time as it is used by the filter bacteria as part of the way they convert ammonia > nitrite > nitrate. That is why in areas where there is very low kH, it is necessary to buffer it in some way. Otherwise the tank is at risk of rapidly exhausting kH and causing pH to crash and the filter bacteria to cease functioning. Even where there is high kH in the water initially, if water changes are neglected for long enough the kH will eventually run out with those same effects - "old tank syndrome".