Steady And Frequent Fish Loss In Community Tank

[crmpicco]

I have had my community tank set up for 18 months now. Over the past 6-8 weeks I have had a steady loss of fish at the rate of around 1 death every 2 weeks.

The most recent to go was an original Neon Tetra from 18 months ago, which had grown to quite a big size.

Before that I lost a guppy a week before that I had reared from a fry.

I religiously change 30% of the water every 7 days (normally a Sunday) and as tomorrow is Sunday and the tank will be due a change, I done some water tests to see what the levels were at. Here are the readings:

ph 7.6
High pH 7.4
Ammonia 0.25ppm
Nitrite 0
Nitrate 20ppm

I'll update my signature with my current stock, as it is out of date at time of posting. My tank is a 70ltr Hagen Tropiquarium.

What could be a possible reason for my frequent fish loss?

 

[Sophie]

In a tank that is 18 months old there should be no Ammonia reading.
Is this from using the API liquid test?  Could it be possible you got it wrong?

 

[N0body Of The Goat]

Even if your sig is now incorrect because of the deaths, that stocking was very high. A 70l tank should be housing ~35-45cm of fish going on their adult size, not the size you acquire them. Your tank would have been fully stocked with your Harlequin Rasboras, Guppies and Endlers.
 
What are the dimensions of this tank? It is almost certainly too small for Zebra Danios, Mollies; Platties; Peppered Corydoras.
 
Crowded tanks increase stress, which lowers immune systems and any contagious illness will rapidly spread through the community.
 
The recent heatwave in the UK could have dropped oxygen levels down too much.
 
Your nitrate levels could be much higher than your readings, I would expect high nitrate levels with such overstocking (although RO water would certainly help), you literally need to shake/bang the nitrate bottles for a good 1/2mins to get reagents back in solution.

 

[Sophie]

When was the last fish death? Did you remove the body immediately after you found it?
Was there any recent additions of fish before the deaths started?
Did you do anything different, anything at all? New decor? Changed some filter media?

I would've thought that even if it is overstocked, something would've happened sooner rather than running fine until 18 months?

 

[wrightt3]

Ammonia should be at 0.
Even small traces can be harmful to fish so that may be why you are having problems. By looking at your signature, you have quite a heavily stocked tank so that's probably part of the problem.
 
First of all, I'd look into rehoming the danios, they need a 3ft tank minimum, some would even say 4ft and for good reason. these fish are extremely active fish!
After that I would look into thinning down your stock a bit.
 
Edit: never mind, already been said by sophie and n0bodyof the goat

 

[crmpicco]

In a tank that is 18 months old there should be no Ammonia reading.
Is this from using the API liquid test?  Could it be possible you got it wrong?

Hi Sophie, yes I used the API kit. I was quite particular about the drps and testing, so I think 0.25 is correct. I thought a slight creep in ammonia towards the end of the "cleaning" week might be manageable. Could this increase be caused by over feeding?

 

[Sophie]

 

In a tank that is 18 months old there should be no Ammonia reading.
Is this from using the API liquid test?  Could it be possible you got it wrong?

Hi Sophie, yes I used the API kit. I was quite particular about the drps and testing, so I think 0.25 is correct. I thought a slight creep in ammonia towards the end of the "cleaning" week might be manageable. Could this increase be caused by over feeding?
 

 
http/www.fishforums.net/index.php?/topic/421488-cycling-your-new-fresh-water-tank-read-this-first/
 
Have a little read here my dear - this will help to explain a bit more on the nitrogen cycle. Ammonia and Nitrite, once a tank is completely cycled should be processed into Nitrate within 12/24 hours.
 
Go and have a little re-test and check the ammonia in different lighting - natural, artificial, against different white backgrounds. I find it very hard myself to determine between a slight green tinge even when I know 100% my tank has no trace of ammonia.
 
Have you started feeding them anymore than normal recently?
(Don't 100% quote me on the Ammonia/Nitrite being converted within that time period, I am unsure myself of the exact reason why there should be no reading of either of these, there just shouldn't )

 

[crmpicco]

Even if your sig is now incorrect because of the deaths, that stocking was very high. A 70l tank should be housing ~35-45cm of fish going on their adult size, not the size you acquire them. Your tank would have been fully stocked with your Harlequin Rasboras, Guppies and Endlers.
 
What are the dimensions of this tank? It is almost certainly too small for Zebra Danios, Mollies; Platties; Peppered Corydoras.
 
Crowded tanks increase stress, which lowers immune systems and any contagious illness will rapidly spread through the community.
 
The recent heatwave in the UK could have dropped oxygen levels down too much.
 
Your nitrate levels could be much higher than your readings, I would expect high nitrate levels with such overstocking (although RO water would certainly help), you literally need to shake/bang the nitrate bottles for a good 1/2mins to get reagents back in solution.

My sig is now accurate and up to date. I should add that a good number of my guppies and players are babies growing up, so they are not fully grown adults.

It certainly has been warm the past 4-5 weeks here in Scotland, but the temperature has dropped now.

 

[Sophie]

I would've thought if it was the temperature it would've been a lot more, within a shorter space of time?