KH buffering - urgent

[Myrkk]

I did a 50% water change in my 200L tank yesterday and put the oak wood back in. The wood has been out since 10th August. Also mopped up most of the weed that floats on the surface of the water.

Today, 3 dead fish and the rest look very stressed.

Tested the water and my KH is 1 - ARGH. All other parameters are where they should be. GH is 4 / 5. Nitrates were 0.5.

Tested the tap water and the KH is 1.

How do I buffer this tonight? Doing another water change is going to make things worse.

I’m concerned I’m going to lose the entire tank of fish at this rate.

 

[Ram419]

Need something like Seachem Alkaline Buffer or API Proper pH to raise the pH and KH. There may be other methods but I don't know them.

 

[Myrkk]

Thanks Ram. I’ve googled and found an entry that says bicarbonate of soda at half a teaspoon per 100l so have popped some in. Hasn’t raised anything but the fish have started to look less stressed, although are still panting a little, are out of the plants and trying to feed. Will take some water down the local fish shop tomorrow am first thing and hope I don’t lose any more overnight.
Strangely it’s the diamond headed tetras that are succumbing, the chilli rasboras and long finned calico bristle noses haven’t died… yet! I’ll be super upset if they go.
The tank is under stocked and generally peaceful..

 

[Ram419]

Very sorry to hear about this. Did the source tap just all of the sudden drop in KH when it wasn't like that before?

 

[Myrkk]

I’m not really sure as we’ve not long moved house and couldn’t find my test kit. I stupidly decided all would be ok for a couple of months with less strict monitoring, it’s been a stable tank for a long time. All seemed ok until I did the water change yesterday and today it’s all gone south.

Interestingly the bristlenoses that had gone quite pale after the move have gone dark again almost immediately the wood was put back in. Wondering if they change colour depending upon their environment, a sort of camouflage thing.

 

[Sir Guppy]

I have heard that certain bristlenoses can!

 

[Colin_T]

What sort of fish are in the tank
Fish from tropical Asia or South America generally come from soft water with little or no KH. Things like gouramis, Bettas, tetras, Corydoras, discus, angelfish, rasboras all do well in water with a low GH & KH.

If your fish started dying after you added the wood, then it might have been contaminated by something that has poisoned the fish. Big (80-90%) daily water changes can usually help, as can adding some activated carbon to the filter for 2-4 weeks.

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Sodium Bicarbonate (baking soda) is available from any supermarket for a few dollars. Whilst it will raise the KH of the water, it will also raise the pH, so care must be taken when using it. A sudden change in pH (either up or down) can kill the fish.

If you want to use Sodium Bicarbonate, add a spoonful of it to a bucket of dechlorinated water and aerate it for 5-30 minutes. Then add a small amount of that water to the aquarium. Wait 30 minutes and check the pH. If the pH hasn't changed but the KH has, that is fine. If the pH has gone up 0.1 or 0.2 points, that is fine but don't add any more until the next day or a few days later.

 

[seangee]

What is the kh/GH of your tap water?
What fish do you have?
When did you last change the water?
My KH is zero and I never have issues, but do regular water changes. I would be looking at what changed first, ie the wood.
FWIW the wood will drop the KH, this is ok as long as you do regular changes.

 

[Myrkk]

18 Diamond headed tetras are the main fish followed by
11 Chilli rasboras
4 (2 are babies that were born in my last tank) Long-finned calico bristlenoses
4 red phantom tetras - the last of my first fish group
2 Black Venezuelan corys - again the last of the first fish I had
A chinese algae eater that I’m looking for.a good home for

That’s my worry with the wood but I brought it over to the new house myself as I didn’t want the chance of any issues. It’s sat safe away from everything until I put it back in. I’m wondering if the microbiome that was on it has rotted and that is causing the issue? However the bristlenoses are feeding on it with no ill effects.

Water last changed Wed, around 50%

No dead fish this am, in fact one that was looking like it was going to die is swimming around, albeit not as great as it could be, hopefully it will recover fully.

Last night
KH 1
GH 4 / 5
pH 6

This am after 1tsp of bicarbonate last night
KH 1
GH 5
pH 6

 

[seangee]

All of those fish (I know nothing of SAEs but you are looking to re home anyway) will thrive in the conditions you reported last night and the chilli rasboras need to have negligible hardness and low pH. I wish my tap water was like that.
I would not mess with the water, just keep up with weekly water changes of 50% or more.

 

[Myrkk]

Thanks Sean. The water up here is very soft and one of the key pieces of advice I got on here when I first started out was stock for your water parameters and life will be much easier. So I did. This has made for an easy life fish wise and I very rarely have issues, in fact this is the first water related issue I’ve had in over 5yrs.

That leaves me at a loss as to why the sudden issue. There’s only one other thing I can think of… we had the wood stove on in the room the tank is in and it gave off a very weird smell. Not carbon monoxide as we have an alarm next to it for that. Wondering if that absorbed into the water? However, we have been using the stove for a few weeks now.

Anyhow, things seem ok’ish at the moment. I’ll keep a close eye and be strict on my water changes. Was going to clean the canister of the filter but think I’ll leave that a few days until I’m sure things are more settled.