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Fish dying when do a water change

Myrkk

Myrkk

New Member
Joined
13 Jun 2024
Messages
18
Location
Scotland
Hi Everyone,
I have a 200L planted tank which is 7yrs old. Moved house last year and every time I did a water change it caused fish to die. They’d be swimming vertically gasping as though they couldn’t get air. pH was 6, hardness was 1, nitrites/nitrite/ammonia all 0. I used to put some bicarb of soda in and it would help a little but it would take a few days for the fish to return to normal.

I therefore stopped doing water changes whilst I tried to figure out the issue.

Last week the heater packed in so the tank had a cold water shock. LFS guy mentioned chloramine (and this forum). I decided to do a small water change yesterday and double dosed the prime. This am all bar 4 of my fish are dead. Nitrites/nitrates/ammonia all 0 and pH 6.

I’m at the point of selling up my tank currently. Any suggestions as to what could be going on? Have added the local water chemistry report the local water people sent me this am when I called them.
 

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  • Water 202303 Rosebery A Last 12 Months.pdf
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Nothing crazy in the report. Are you 100% sure your tap isn’t coming from a well?

You need to start ruling things out.

  • Test for ammonia nitrates etc
  • Do a water change with aged water
  • Do a water change with boiled water

If you water hasn’t been changed in a very long time, fish can be weakened by this.

When you change water is the water a good temperature? Is it a slow change? How much detritus is in the water?

Honestly, I’d be doing a 100% water change as my feeling would be it’s the aquarium that’s up, or the delivery method.
 
Can you provide the info below especially a FTS? It might make it easier for folk to help diagnose what the problem is ;)

1. Size of tank in litres.
2. Age of the set - up.
3. Filtration + Media/Sponges.
4. Lighting and duration.
5. Substrate.
6. Co2 dosing or Non-dosing.
7. Fertilizers used & Ratios.
8. Water change regime and type.
9. Plant list + When planted.
10. Drop Checker.
11. Inhabitants.
12. Full tank image & Surface image.
 
Thanks. Not a well, deffo a reservoir.
I’m a bit damned if I do or don’t . I change they die, I don’t they’re ok but water quality is degrading.
I haven’t changed how I do the water changes in the last 7yrs so I doubt it’s that.
No detritus showing in the water, there’s usually leaf litter on the sand at the bottom but again that’s been like that for 5 of the 7yrs. There’s less leaf litter than normal currently as I haven’t popped anything new in in case it tips the tank over the edge

I think I’ll go for aged water as a starter.
 
Hi @Myrkk.

My water supply is also Roseberry A. Chloramine isn’t being dosed into that supply regularly. In fact, I top off my tanks and fill up my pond with water straight from the tap without adding a dechlorinator. I’ve forgotten it once or twice on a 50% water change (including recently) and no negative effects have been seen. While this isn’t good practice it does add food for thought on your problem.

I think there’s something else going on here.
 
Was your previous house in the same area? Could it be something up in the plumbing with the specific tap you are using or with the house in general? Like a contamination that is at your house level only? Do you have a header tank that's contaminated?
 
It would be nice to have more info, as per Tim Harrison's post.

We don't even know how much water is being changed.
 
richardcunliffe said:
Was your previous house in the same area? Could it be something up in the plumbing with the specific tap you are using or with the house in general? Like a contamination that is at your house level only? Do you have a header tank that's contaminated?
Click to expand...

Just thinking the same, perhaps the hot water tank has an issue? (If it exists)
 
Hi I'm not a great lover of Prime...there has been reported issues with this water conditioner!

Could well be a combination of dosing Prime and osmotic shock!
Do smaller water changes over a longer period of time!
That's my hunch....this issue can rear its head in low PH and long established aquariums!
Ditch the Prime....leave the water change water overnight in a bucket then add in the morning!
 
Prime is concentrated so doubling the dose is probably not good. Checkl the water company for any work in the area, we have been there,when your water is cut off ,or a sudden discoularation of your tap water appears.,Water companys don't always report this
 
I would say, oxygen content of new water (try more aeration when changing water), temperature difference of new water, or your disturbing something in your tank when you do water changes and this is releasing toxins.

Water going in appears ok, unless its coming from a storage tank.
Temperature difference is easy to check as your doing the water change.
Disturbing something? Try just changing water and not disturbing the sediment as a one off. If ok after say 3 days disturbe the sediment but don't change the water unless the fish are showing distress.
The fish are gasping & vertical, improving after a few days suggests the tank conditions improve with time & are ok.
 
Prime depletes oxygen levels....therefore if you have very low O2 that could cause a problem if you are double dosing Prime!
 
1. Size of tank in litres. 200L
2. Age of the set - up. 7yrs, tank moved Aug 10th last year so in new location since then. Replanted at that point with some of the older plants. Is a work in progress re. Deciding how to landscape it currently.
3. Filtration + Media/Sponges. Canister system Crystal Profi 920 with white wool, carbon sponge, white sponge, noodles
4. Lighting and duration. Fluval LED light on for 8hrs of the day on a daylight spectrum
5. Substrate. Cream sand with a smaller sand underneath
6. Co2 dosing or Non-dosing. No CO2 dosing, buy easy to look after plants.
7. Fertilizers used & Ratios. Rarely use Plenish at 3/4 of a cap to tank, maybe once every couple of months.
8. Water change regime and type. Not at the moment as this happens every time, usually to a lesser degree.
9. Plant list + When planted. Twisted vallisenaria, 4yrs old, replanted last august. Hygrophila Siamensis , 5yrs old, replanted last august. A lot of duckweed, came with a fish many years ago and has taken over, scoop handfuls out every few months. Some mixed leaf litter, not added any for a while so mostly broken up and digested
10. Drop Checker. - what is this?
11. Inhabitants. As of today 3 long finned calico bristlenoses, 1 x black venezualian cory
12. Full tank image & Surface image. Will sort this out tonight
 
Myrkk said:
What is old tank syndrome?
Click to expand...

Over time nitrate accumulates without sufficient water changes and one day, becomes toxic.

Carbonates can get depleted over time, so one day your tanks water is acid.

Dissolved oxygen can crash. Which is normally a compound effect from the above, with other things. Then your fish die.

Plus others, but basically always do a regular water change.
 
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