Mysterious Disease Killing My Fish

[andyG44]

As you know I have had a lot of fish deaths int he past few weeks in my community aquarium that was initially stocked with over 43 fish.
 
In the beginning I thought it was velvet, there were clear symptoms on couple of fish. I treated with the 6 day cycle as mentioned on the bottle.
 
But then I had other fish dieing as follows. First the fish looks lethargic. From being a vivacious, curious, playful, exploring fish, it just becomes lethargic. He swims slowly. Depending on the level of this mysterious disease he sometimes swims only to avoid obstacles. As the disease progresses he starts to bump on obstacles, been taken by the currents too. Sometimes other fish start picking on him and he evades as a last resort, as the disease progresses he does not even do that. Eventually the fish stops being active, is being taken by currents, and even in the small isolation tank he does not move but only to breath (as seen with a magnifying glass), eventually the breathing stops.
 
The whole cycle from very active fish to showing first symptoms to dieing lasts for less than 24 hours.
 
Even though I have plenty of fish this disease only kills them one at a time - I do not think I had more than one fish sick at the same time.
 
My tank parameters are OK, nothing significant to show.
 
Today after feeding, I am observing the male molly is being rather slow, quite unlike him, but he is stil inquisitive, I just put my finger on the glass and all the three mollies came up to it.
 
But I know this disease now, and I know "slow" fish typically means dead fish in 24 hours.
 

 

[Ch4rlie]

We're going to need some more information am afraid.
 
Starting with tank size?
 
What are the exact parameter readings you have been getting with the tank water?
Tap water parameters may be of some help also.
 
What is your stocking and any new stocking added recently?
 
Tank temperature?
 
Your usual water change routine?
i.e once weekly or more and percentage of water changes, add tap safe/dechlore or not
 
Any other symptoms at all?
red gills, rapid breathing beforehand, swimming erratically, spots/markings, swollen/shrunken stomach etc
 
Have you made any changes to the tank at all recently?
i.e new substrate, different fish food, new plants or decor etc
 
And lastly, a picture of any fish showing symptoms may be of some help.
 
Quite a few questions, I know, some are proabably pretty obvious but the more information and details you can give, the better for us to try and help you.

 

[BiggTexx]

We're going to need some more information am afraid.

Maybe I can help out Charlie...
 
From another thread:

14 guppies
6 galaxy rasbora
2 dwarf gouramis
4 black phantoms
6 neon tetras
4 mature gold barbs
3 mollies
a handful of snails (believe to be bladder snails)
2 plecs, one is 2 years old and around 2-2.5" the other is newer and 1-1.5"

These are in a 180L and we believe the two plecos are 'commons'.
 
Readings as of last update:

 
Ammonia : 0.00-0.25
Nitrites : 0.00
Nitrates : 40-80
Tap water Nitrates : 20-40 or more (hard to tell the colours)

 
Temp was mentioned in another thread as 25-26C.
 
Recent additions to your tank (living or decoration):

 
3 live plants and lots of new fish of all types

 

[Ch4rlie]

Thanks BiggTexx, that helps a lot.
 
Its that last answer - "3 live plants and lots of new fish of all types"
 
That may hold some clues or answers as to why OP's fish are dying, wonder if these fish dying are the new ones or perhaps they bought something in to OP's tank that affects his stocking.

 

[Byron]

The other thread BiggTexx mentions is here:
http/www.fishforums.net/index.php?/topic/438122-common-green-algae/
 
The tank is overstocked, and the fish species are shoaling so there is more stress from insufficient numbers, plus the high nitrates.  I don't know what the water change schedule has been up to now, but cyanobacteria appears to be another issue.  We don't know what was added to deal with the alleged  Velvet, but that probably factors in.  Ammonia is present constantly, though admittedly at a very low number, but it probably plays a part.  Water parameters seem to have fluctuated several times, due to tap water/RO water mixes or not being mixed for water changes.  I believe Andy realizes things better now, and we are progressing.  But after all this, fish deaths should not be a surprise.  And the symptoms I would suggest are more likely due to the water issues than disease, though this is only a guess.
 
Byron.

 

[Ch4rlie]

That does make a lot of sense now that information has come to light.
 
Always better to have as much information and details as possible to do a process of elimination.
 
Very correct in stating tank is well overstocked and will have an impact on water conditions.
 
Seems there are a couple of issues, but one by one all these issues are solveable pretty easily.

 

[TwoTankAmin]

When ammonia or nitrite are doing damage to fish, especially killing them, they do not go one at a time. However, I have seen diseases that are like that but its notlimited to one per day every day. Sometimes its one or two went and then some days it was a few more. I watched a tank of newly imported altums do this. 21 fish dead in about 1 week, It took about 8-10 days before the first death after the fish arrived. Unfortunately, they were all dead before I had time to try more than dosing One antibiotic.
 
First the fish would separate from the rest and hang out near the bottom and be lethargic. Then it would more to the surface where it died. Some doseases are like that they take a bit of time to move from fish to fish whereas ammonia and nitrate affect them all at the same time.
 
As Byron notes there are other issues in the tank, but I doubt they were the root cause, they only are exacerbating things.
 
The one thing I hope readers take from this thread is the value of having and using a quarantine (Q) tank.

 

[andyG44]

Thanks guys, here's the most recent update.
 
Two days now without deaths or disappearing fish. I count them every morning. The "sick" molly seems to be OK, I was just being paranoid. Touch wood.
 
There is a neon tetra that is not keeping with his mates and instead is wandering around elsewhere. I wonder why.
 
The current stock is:
 
180 lt tank
20+kg gravel
temp : 25C-26C
 
3 live plants
13 guppies (lost 2 over the past few weeks)
6 neon tetras (lost 9)
6 galaxy rasboras
4 black phantoms (lost 3)
3 mollies
4 gold barbs
2 dwarf gouramis
[ 5 tiger barbs (lost 2-3) - and remaining were returned because they were too aggressive and were harassing other fish ]
2 plecs
plenty of bladder snails
 
total fish remaining: 40 + snails
fish lost in last month: 15 or so
feeding : once a day except Wednesday, tetramin flaks and some other semi-sinking pellets
water change : when levels drop (I lose around 1 inch a day as there is no cover yet), when ammonia clearly exceeds 0.25 - due to using an expired API test kit I was getting wildy incorrect results and believed the tank to have crashed and was making large daily water changes.
 
I believe there is a disease at play since typically only one fish ever got sick at once, although I did lose two on a couple of occasions
 
Velvet was treated with Waterlife Velvet + Fungus treatment, it has an 6 day treatment cycle.
 
Two days now no deaths, but I know it all looks good and then it strikes suddenly.