Series of deaths in our tank...

Sephiroth329

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However none of the deaths seem to be the same,

Tank Overview:
Running for 1 year 5 months
80L Tank (though bought thinking it was 100L, advertised secondhand incorrectly) possibly over crowding
Fluval 306 external Filter
Fish in the tank leading up to this post:

1 Pleco
4 Cardinal Tetras
4 Endler Guppies
3 Mollies (unsure on exact breed)
2 Gourami (Pearl and Golden)
7 or 8 Platties (sods keep breeding and can't always keep count)

A number of water tests done over the weeks that this has happened in and all reading have been:
NH3/NH4 - 0
NO3 - 0
NO2 - 0
pH - 6.5/7 (slightly unsure on colour test)
KH - 80
GH - 180

also had the water tested at a petstore and they said it all looked ok.

First death was a molly in the first week of October, she had been ill looking previously in September, we treated the tank with Anti Internal Bacteria and got better, however while we were away on a holiday we got back and she'd taken a turn and died withg signs of dropsy (scales all popped up). She had been shimmying on the spot a lot before the turn.

Another molly started shimmying a few weeks ago and her gills going 100mph like she was panting, at the same time we noticed the pearl gourami had a sore over his mouth which we were told could be fungal so we bought Primafix and Melafix. The molly died a day after we started treatment (no signs of dropsy this time though) along with 2 tetras which was unexpected as they looked ok. We continued with the Pri/Mel as the gourami was looking better but had not been eating as much for the past coupe of days which concerned us.
We thought maybe the treatment for the molly had just started too late to save her.

Well today we did a 25% water change as instructed by the medication as we had done a weeks treatment when out of nowhere the gourami suddenly (an this is before our eyes, suddenly) started floating in the water.It had lost all buoyancy and directional control. We thought he was dead but then started darting around panicked and desperate, he would then stop and float, over and over. His eyes had also gone jet black all over. (normally just the black band of his pattern carried on through the eyes). This lasted 5 or so minutes and before we could set anything up for him he died.

So in 4/5 weeks we have lost 2 mollies, 2 Tetras and a Gourami. What has happened! nothing like this has happened in the time we've had the tank. The only things added were some plants from a respected store.

Is there anything we can do to make sure nothing else gets ill (preventive treatments) or anything people can think has caused this

I know this is a long post so i do appreciate it if you read it all.

Cheers,
Dave
 

Byron

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I am not going to "diagnose" a disease per say, as this is very difficult even for experienced aquarists and I have very little experience with disease (I've been fortunate in my 20+ years in the hobby). I do however see a couple issues which I will mention, but please don't read into it that I am saying this or that is the cause; these issues are simply more stress on fish and stress itself causes 95% of disease so they are factors, whatever the actual "disease" may be, or of course there may not be one.

First, you are correct that this tank at 80 liters (20-ish gallons) is too small for some of the named fish, especially gourami and mollies. Please do not get more of either, as they will not be at their best. Mollies attain 3 inches (males) and 5+ inches (females) and need much more space. The gourami get 3-4 inches, and the Gold is (or can be) a very nasty fish. Males are territorial, the Pearl more peaceful though individual fish can vary from the "norm." But the Gold species is very territorial and frequently aggressive. On this, have you ever seen interactions involving either gourami?

The other problem with mollies is the GH and pH. Livebearers need moderately hard or harder water with a pH above 7 (i.e., basic, not acidic). Your GH at 180 ppm (10 dGH) should be OK for most livebearers but unfortunately not mollies who need it harder. And the acidic pH is not good at all for mollies. Shimmying, fungus, extended scales is a sign of the GH/pH issue, though other things can cause this too. But here, the GH/pH has not helped even if it is not the actual issue--and I won't hesitate to say it may well be the issue.

The gourami mouth issue may not be related, I have seen fish with similar "growths" and generally leave them alone. Guessing and adding medications can make things far worse unless it is absolutely what is needed.

Another suggestion...when something occurs like here, the first thing to do is a major water change, up to 70% of the tank volume. Use a good conditioner. I have more than once resolved "unknown" problems just by doing a major water change. I wouldn't use either Melafix or Primafix (I tried these once and the fish had an extreme reaction); such "catch-all" remedies rarely do anything beneficial as they are too broad-range, and all of these substances added to the water get inside the fish by osmosis, so they can be stressful. And when there is an issue, stress is something you want to lessen, not increase.

So at this stage, I would do some water changes, use a good conditioner, and forget the treatments. Wait until fish are seemingly "normal, with no further deaths or signs of trouble, a few weeks beyond that, before considering more fish. But before that, depending what fish are left, you might want to remove some of the survivors. Female livebearers will mean hundreds of fry and in so small a tank this is obviously going to cause more problems as they appear. The molly should go, if it doesn't follow the others.

Byron.
 

StevenF

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Well today we did a 25% water change as instructed by the medication as we had done a weeks treatment when out of nowhere the gourami suddenly (an this is before our eyes, suddenly) started floating in the water.

Loosing a fish right after a water change worries me. I am concerned that something about the water that was added harmed the fish. Before doing a another water change I would recommend testing your tap water for NH3/NH4, NO2, HO3, PH, GH, KH. Any differences between your tap and tank water might be a potential cause. Big changes of PH, KH, and GH could harm the fish.

Also do you add anything to your tap water before adding it to the tank (water conditioner, fertilizer, etc). If so list the product and how you dose it. Verify you are dosing it correctly.

Also excluding the water changes associated with the medications you used, how often and typically how much water do you typically change out?
 

NickAu

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also had the water tested at a petstore and they said it all looked ok.
Most pet shop employees wouldn't know their elbow from their big toe. Next time ask them for the actual numbers.
 
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Sephiroth329

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Cheers for the messages, we did an extra 50% water change the following day and i'll get something to make the water more basic (we do put aquarium salt in as we read/we told that Mollies need this but didn't know about the pH)
So far no more deaths or ill looking fish so fingers crossed. We use Interpet Bioactive Tapsafe for water treatment when doing changes. this is added to every bucket we added.

On a side note, does anyone have any knowledge on why our mollies keep getting up close with our heater. The water is set to 25C/77F which from what i know should be fine but they have got sore mouths from just swimming in front of it with their mouths pressed up on it. one has seemed to stop doing it now but the other is there on a regular basis. no other fish in the tank do this. only ever mollies

Cheers,
Dave
 

Byron

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Cheers for the messages, we did an extra 50% water change the following day and i'll get something to make the water more basic (we do put aquarium salt in as we read/we told that Mollies need this but didn't know about the pH)
So far no more deaths or ill looking fish so fingers crossed. We use Interpet Bioactive Tapsafe for water treatment when doing changes. this is added to every bucket we added.

On a side note, does anyone have any knowledge on why our mollies keep getting up close with our heater. The water is set to 25C/77F which from what i know should be fine but they have got sore mouths from just swimming in front of it with their mouths pressed up on it. one has seemed to stop doing it now but the other is there on a regular basis. no other fish in the tank do this. only ever mollies

Cheers,
Dave

The molly behaviour, assuming your data on the temp is correct, is most likely another aspect of their distress over the water. When we are unwell, we try to keep warm. In a round-about way, this is similar.

I suggest you not go messing with water parameters, but instead select fish suited to those you have. Water chemistry is a very complex issue. Accommodating the mollies will mean water unsuited to the other mentioned species. There is no "middle road" to speak of. Plus, there are times when more frequent and/or larger water changes may be needed, and having to prepare water ahead makes this very difficult.

You mention salt. Salt is tolerable to mollies (unlike almost all other freshwater fish) but this is only part of the mineral aspect. But while salt would perhaps help the mollies here, it will cause serious problems for the tetras, gourami and pleco. So again you are helping one fish but harming several others.

Byron.
 
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