Diagnosing a Massive Die off

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OpalAquarium

Feeder Fish
MFK Member
Nov 6, 2015
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Hello fellow aquarists ,

Im hoping you can help diagnose the series of F**kups I must have made to wake up to my 75 gallon tank dead this morning. I understand my actions may seem obvious to some of you after reading, im hoping you can be kind and help inform me so this never happens again.

Background
I have been keeping fish for 2 years now, this was my third tank
I had not been running water tests as tank has been stable for so long (First mistake)
Tank was fully cycled and running for close to a year.
It is a planted 75 gallon with A large stump, Texas holey stone, and zebra rock
Filtration is two Fluval 305 each one is rated for 70 gallons
Substrate is seachem flourite black sand
Lighting is a double T5 fixture and a T8 fixture running a mix of plant and full spectrum bulbs
I use a 3 stage RO system to filter my incredibly hard tap water ( Barracuda)

Stock
1 Black ghost knifefish 10 inches ( dead)
2 Pakistani loaches, yoyos, 4 inches ( 1 dead, 1 hanging on)
1 Marble loach , 2 inches ( dead)
5 Gaint danios , 2-4 inches ( 4 dead, one hanging on)
2 Marci rainbows, 4 inches ( dead)
3 Bosmani Rainbows, 3 inches ( dead)
1 Flying fox, 4 inches ( dead)
1 Farowella ( alive)
4 Nerite snails ( maybe 2 alive)
Infestation of MTS

Recent activity:

2 weeks ago : deep clean, removed lots of overgrown plants, scrubbed rocks outside tank
Deep clean of filters while preserving biological media in bucket with airstone
No issues

1 week ago: weekly 20 percent water change and waste siphoning
Noticed mouth fungus/ white patch on Flying fox mouth, Isolated in mesh breeder started dosing melafix and Pima fix with additional stresscoat, did daily for 5 days
removed carbon from filters
No issues

Last night
Weekly water change, noticed RO system filters are in need of a change but water should still be good
Treated water with Stress coat , Stress zyme, tiny bit of prime , 15 ml of liquid C02, 60 ml Pimafix and Melafix
Still no carbon in filters

Observations after:
I didnt think much of it at the time but noticed the rainbows near the surface with the danios, I thought they were just looking for food from the remaining stuff floating in the tank. Fed freeze dried blood worms and flakes

This morning:
I wake up to find most of the tank dead, salvage the 4 survivors and move to another tank.
Test water to find water is more acidic than normal, and that nitrates and nitrites are high, no chlorine registers, water is of a medium hardness.


Did some combo of my melafix pima fix treatment without my carbon kill my nitrifying bacteria ? What the hell did i do ?!

IMG_20151026_091859152_HDR.jpg
 
how much surface agitation do you have in that tank?
Melafix and Pimafix are both oil based, and can create an O2 barrier on the surface, and without any agitation on the surface your O2 depletes quickly.
my next guess is you say you have an infestation of mts, which as history dictates, if left unchecked will cause one nasty recycle of a tank in no time flat.
 
Both of my filter heads exit out near the surface, so there is a fair amount of water movement but i added enough water this time that they were slightly covered, instead of making bubbles like they normally do it was just moving it around. I do have 2 air-stones that activate at night
 
OpalAquarium said:
Both of my filter heads exit out near the surface, so there is a fair amount of water movement but i added enough water this time that they were slightly covered, instead of making bubbles like they normally do it was just moving it around. I do have 2 air-stones that activate at night
Click to expand...
my guess is a mini cycle coupled with O2 loss.
 
predatorkeeper87 said:
how much surface agitation do you have in that tank?
Melafix and Pimafix are both oil based, and can create an O2 barrier on the surface, and without any agitation on the surface your O2 depletes quickly.
my next guess is you say you have an infestation of mts, which as history dictates, if left unchecked will cause one nasty recycle of a tank in no time flat.
Click to expand...

I spent a good amount of effort last night siphoning up as many of the mts from the sand as I could. Can you help explain the mechanism through which the mts cause the recycle? I had been trying to treat the infestation via reducing the food and more frequent cleanings
 
OpalAquarium said:
I spent a good amount of effort last night siphoning up as many of the mts from the sand as I could. Can you help explain the mechanism through which the mts cause the recycle? I had been trying to treat the infestation via reducing the food and more frequent cleanings
Click to expand...
right there could be your reason. MTS are substrate burrowers, so what looks like several hundred could be several thousand in a tank with enough food.

reducing food and cleaning more solids out of the tank would cause a massive die off of the infestation, resulting in 100's of snails in your substrate dying and decaying. that would cause your biofilter to be well overburdened by the influx of ammonia and nitrite.
 
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