Help Mystery Problem Killing Shrimp And Adult Discus

  • #1
HI guys! I need some help to solve a mystery that’s been going on in my tanks. I will list the parameters for the 6ft tank but there are 3 tanks the problem:

All my shrimp died from a mystery disease and now my favourite 10” discus mysteriously ad QUICKLY died. They symptoms of the discus was that she seemed to have some colour loss on her side and she was very lethargic but had a couple of swims across the tank while I was trying to get a hospital tank heated ready for her, she then just stopped breathing but she still had lots of colour and wasn’t dark but she was a blue discus and I’ve noticed they don’t seem to be able to turn dark?? I had watched a cherry shrimp who stayed red for quite some days while parts of it turned white. It was like it was still alive but paralysed... here is the background info leading up to the discus death.

As mentioned we have 3 tanks a 6ft and 2 x 2ft. One 2ft had cherry shrimp in it and I was taking plants from the 6ft that were dying because they had so much algae on the leaves and planting them in the shrimp tank and the shrimp would clean them and I would keep swapping plants back and forth. We had placed large feeder shrimp in the 6ft as a clean up crew and thy were having a great time. I also purchased some black worms and started a black worm culture and was occasionally feeding the 6ft tank of 10 discus some blackworms in a cone. I was doing large 50% water changes on the 6ft every 2-3 days as this makes the discus grow well (I’ve since discovered that very good water parameters will do the same job) then I would fill the 6ft with our rain water tank and then siphon some 6ft water into the 2ft cherry tank and then change the black worm water with the cherry shrimp water everyday. After about 3 weeks I was vacuuming the gravel in the 6ft and there was no shrimp... not one... that’s weird. I took out all the ornaments and plants and gave it a much better vacuum and sure enough no shrimp and quite a few bodies that were just shells or parts of shell... that’s weird. Then come to think of it... there didn’t seem to be many cherry shrimp and they weren’t swimming around much ... hmmm so I took the plants out and there was about 5 shrimp out of 15 left, I gave the gravel a good vac and changed the water straight from the rain water tank and put the plants back, they started swimming around again but the next day they were back to slow... I kept changing the water (small changes) in the cherry tank but they just kept dying slowing down and standing still staying red but parts turning white then death. I started separating all the tanks when I refilled I mean I stopped refilling them from one another. I thought perhaps planaria because the gravel was quite dirty, my partner over feeds the 6ft. So I’m now doing daily gravel vac in the 6ft and just changing about 10% water just however much it takes to vacuum the gravel then fill up with rainwater. I have a dipstick perimeter tester which has been saying nitrate is high around 40pp I’ve also banned partner from feeding fish and I’m feeding them only what they consume. The night before the discus died I was supposed to do a gravel vac but decided to to it the next day (as I was doing it daily) and when I did the vac after the discus died I realised that the filter had been off for a day. I’ve done a large change after that and all the other discus are fine. But why did the shrimp die??? And any idea on the discus? We got 5 feeder shrimp to test the 6ft after all the cleaning and they had disappeared by day 2. Any ideas?? Thanks


What is the water volume of the tank? 600litres

How long has the tank been running? 7 years

Does it have a filter? Canister filter

Does it have a heater? Yes

What is the water temperature? 28 degrees Celsius

What is the entire stocking of this tank? (Please list all fish and inverts.)

8 adult discus

2 adult peppermint Bristlenose

3 3cm baby peppermint Bristlenose

5 Congo tetra

6 rummy nose tetra

2 panda Cory nearly adult size


How often do you change the water? Every day

How much of the water do you change? Enough to vaccine all the gravel about 10%

What do you use to treat your water? I don’t need to, it’s rain water

Do you vacuum the substrateor just the water?

Vacuume and under ornaments too

*Parameters - Very Important

Did you cycle your tank before adding fish? Yes

What do you use to test the water? Test strips

What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.


Nitrite: zero

Nitrate: 40pp

pH: 6.5-7


How often do you feed your fish? 3 times a day

How much do you feed your fish? Enough they consume it all

What brand of food do you feed your fish?

Do you feed frozen or freeze-dried foods? Frozen blood worms, live blackworms, feeze dried blackworms, fish flakes, algae wafers

Illness & Symptoms

How long have you had this fish? About 6 months

How long ago did you first notice these symptoms?

In a few words, can you explain the symptoms? See above and attached photo

Have you started any treatment for the illness?

Was your fish physically ill or injured upon purchase?

How has its behavior and appearance changed, if at all?

Explain your emergency situation in detail. (Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now)


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  • Thread Starter
  • #2
Ammonia is also zero
  • #3
I'd say it was the nitrates that killed both the shrimp and the discus.

Shame because that was a beautiful fish.

Both discus and shrimp require low nitrates, I would aI'm for <10
  • #4
Yeah it wasn't likely a massive PH swing either, hmm...
  • #5
And perhaps that "feeding" 'em 3X per day didn't help to diminish the Nitrate levels either... : ( iscus and shrimp are very sensitive to water parameters etc...
  • Thread Starter
  • #6
Thanks guys every time I turned around my partner was feeding them, now we’ve had some deaths he’s taking it more seriously and staying away from the fish tank. I’ll keep on with less feeding and daily gravel vacuum the levels are slowly coming down. Also thinking of getting some purigen do you think that would help?
  • #7
I wouldn't bother with purigen. I'd just ensure that my water changes are keeping the nitrates <10ppm.

Water quality is normally about filtration in relation to biomass, and water changes.

You mentioned your tank is 6 foot long. How many gallons does it hold?

What is the make and model of your canister filter?

Do you have any additional filtration?

How often do you do water changes, and what percentage do you change?
  • Thread Starter
  • #8
The canister is a biopro 2200 litres per hour and the tank is 600 litres (I’m in Australia) I’m doing water changes everyday for the last 2 weeks just about 15% however much water it takes to vacuum the gravel but I’ve just amped it up to 1 day vacuum and small water change and the 2nd day vacuume and 40% water change. I did clean the filter out and the nitrates seem to be coming down. I also have 3 sponge filters in the tank attached to air
  • #9
The canister is a biopro 2200 litres per hour and the tank is 600 litres (I’m in Australia) I’m doing water changes everyday for the last 2 weeks just about 15% however much water it takes to vacuum the gravel but I’ve just amped it up to 1 day vacuum and small water change and the 2nd day vacuume and 40% water change. I did clean the filter out and the nitrates seem to be coming down. I also have 3 sponge filters in the tank attached to air

OK. You're tank is a little over 150 US Gallons, and your filter is rated at 3.6 times turnover per hour.

You're a little under optimum for filtration. I would consider adding a second canister.

[Edit: just noticed your 3 sponge filters - so as long as these are regularly cleaned you may already have enough filtration]

If that's not possible then regular (every two weeks) canister cleaning, and regular 50% (every week) water changes should do it.

As it's Discus maybe vacuum twice a week. Once with the water change and once mid week.

But you'll have to experiment and see what works for you. The key is clear water and low nitrates.
  • #10
Have you gotten everything sorted now? Still working on it?
  • Thread Starter
  • #11
I did a butt load of water changes (all shrimp died) and left the plants in and added a hang on back filter and air stone. Parameters went to 0. Just added more shrimp and some have died after a few days not many, about 3 from 50. Same thing it looks like a shed but it’s a clear squishy dead body. Did a big water change last night and everyone looks ok now...
  • Thread Starter
  • #12
The discus in the 6ft are fine now but still a ways to go on the nitrates, been doing daily water changes and vacuume gravel and cleaning filter more often. Just rinsing all the out

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