Help! Lots Of Dead Fish After Water Change :(

[quarryman]

I have a very (well up to now) healthy tank.

3 Red Eye tetras
6 Rummy noses
4 Blind Cave Fish
4 Zebras

Over the last 2 years its very rare to have a fish die.

Yesterday i changed the water as normal (done every 3 weeks) and changed the black Juwel filter sponges. They were about 3 months old.

This morning I woke to find ALL 6 Rummy Noses dead. They have been our hardiest fish so far, 2 years old.

Done a water test:
PH 7.5
NH3 0
NO2 0.8
NO3 (Nitrat) 20-25

The NO3 seems very high.

Can someone help with what I should do now? Should I change the waater immediately?

The water itself doesn't look great. Some stagnant bubbles and very subtle oily film that i don't think i'd noticed before.

I tried to take some pics:

 

[rdp50734]

You say you changed the sponges, why? By removing the sponges you have removed some of the beneficial bacteria. You only need to take the old sponges out and rinse them in old tank water and put them back. You only need to change the sponges when they are falling apart!

Your NO 2 should be 0, so you need to water change to get it to 0

NO 3 is fine.

Bubbles could be from low water flow around the tank, what filtration are you running?

 

[FreedomFighter]

Your nitrate is fine, beyond fine.

Those bubbles ar more than likely just bubbles, you also have live plants that will add to these bubbles.

Have you disturbed the substrate? There is a slight possiblity of a buildup of anaerobic bacteria which can be bad. Does it smell eggy at all?

I'd be more concerned over the Nitrite NO2 being 0.8 after a waterchange. I think you may need to increase how often you WC, and I would start by doing another one today to make that 0.8 into 0.

Also, just to make sure, when you changed the filter media, you didn't change all of it in one go, right?

 

[quarryman]

Thanks for the replies.

Ok i've just changed the water again 1/2 tank and NO2 is a bit lower but not ideal. So I should keep changing it then?

I also changed tested the water straight from the tap and both NO2 and NO3 are pretty much 0.

I didn't change all the filters, just the black one. I think i have 2 black ones, 1 green, 1 coarse blue and 1 fine blue. I change them 1 at a time, when required but never all in one go.

As to why I changed them at all. I'm just following the recommended change frequencies as per the Juwel instructions here (page 4).

 

[the biffster]

did you wash any of the sponges
out other than in old tank water

 

[FreedomFighter]

Ah, so you just replaced the carbon. Thats no big then, no worries there.

So, I have to admit, i'm at a loss. The only thing that comes to mind is a possible NO2 spike overnight. I don't think you've done anything wrong, and aside from the 0.8 nitrite then there's not a whole lot wrong with the tank at all.

You haven't been medicating for anything at all?

Sorry I can't help any more than that. Oh and, you shouldn't need to do another water change now for a while. Out of interest how big is the tank? Depending on tank size i'll suggest more often water changes, but thats it. I hope you get no more losses.

 

[rdp50734]

Thanks for the replies.

Ok i've just changed the water again 1/2 tank and NO2 is a bit lower but not ideal. So I should keep changing it then?

I also changed tested the water straight from the tap and both NO2 and NO3 are pretty much 0.

I didn't change all the filters, just the black one. I think i have 2 black ones, 1 green, 1 coarse blue and 1 fine blue. I change them 1 at a time, when required but never all in one go.

As to why I changed them at all. I'm just following the recommended change frequencies as per the Juwel instructions here (page 4).

Dont bother changing the sponges as there is no need to! Only when they start falling apart! Its always in the guidelines to change them but it is by no means needed! Its a way they keep money coming in!

You need to keep doing water changes to get your NO2 to 0.0 Nitrite is just as toxic to fish as Amonnia.

 

[quarryman]

did you wash any of the sponges
out other than in old tank water

No i didn't wash any of the sponges, in tap water or otherwise.

Ah, so you just replaced the carbon. Thats no big then, no worries there.

So, I have to admit, i'm at a loss. The only thing that comes to mind is a possible NO2 spike overnight. I don't think you've done anything wrong, and aside from the 0.8 nitrite then there's not a whole lot wrong with the tank at all.

You haven't been medicating for anything at all?

Sorry I can't help any more than that. Oh and, you shouldn't need to do another water change now for a while. Out of interest how big is the tank? Depending on tank size i'll suggest more often water changes, but thats it. I hope you get no more losses.

Yes, it was just the carbon sponges.

The tank is 75L.

I also always add 2 drops of stress coat after a water change. Been doing it for a couple of years now and have seen no issues, so don't think that is related.

Thanks for the replies.

Ok i've just changed the water again 1/2 tank and NO2 is a bit lower but not ideal. So I should keep changing it then?

I also changed tested the water straight from the tap and both NO2 and NO3 are pretty much 0.

I didn't change all the filters, just the black one. I think i have 2 black ones, 1 green, 1 coarse blue and 1 fine blue. I change them 1 at a time, when required but never all in one go.

As to why I changed them at all. I'm just following the recommended change frequencies as per the Juwel instructions here (page 4).

Dont bother changing the sponges as there is no need to! Only when they start falling apart! Its always in the guidelines to change them but it is by no means needed! Its a way they keep money coming in!

You need to keep doing water changes to get your NO2 to 0.0 Nitrite is just as toxic to fish as Amonnia.

Really? So I can get away with just a rinse? Is it a case of just a visual inspection coupled with a water change to see if a filter sponge is doing its job?

anyway, changed a good bit of water now and the NO2 is down to 0.4. I'll give it a few more hours and then change some more water.

Thanks for all the help guys. Hopefully I don't get any more losses. It was strange that ALL my Rummy Noses died though - they must be very sensitive to Nitrite.

 

[FreedomFighter]

Well, I guess from here the only advice then is, up your regulat water changes to - every 2 weeks.

And make sure when you do these water changes, that you take out the sponges from your filter, and just give them a quick rinse out in the old tank water, this should keep your filters pretty clean and your bacteria healthy.

Figers crossed for no more losses.

 

[rdp50734]

Do water change 15-20% per week!

Rinse the sponges in tank water when you are doing a water change. You only need to do this once a month or when you notice reduced flow! Only change them if they are literally falling apart and then its only one sponge per week.

Keep changing the water until you hit 0.0 then check daily for any increase fotr the next week or so.

I hope you don't loose any more fish! Any questions please ask and we will do our best to help! When you hit 15 posts you can use the PM function! Also feel free to PM me if needed!

 

[Tolak]

What are you using to treat the replacement water, and how much are you using?

 

[quarryman]

What are you using to treat the replacement water, and how much are you using?

thisstuff.

2 caps of it.

 

[quarryman]

Also, in a strange combination of events we just discovered we a have a baby fish in the tank! The first we've seen in 2 years of having the tank.

What is the best way to keep it safe? I've put it in a glass for now. Should i keep it separated in the tank somehow?

 

[rdp50734]

Breeding net £4 from LFS for the babies.

What Tolak meant was are you using a de-chlorinator? Which one and how much?

 

[Tolak]

What you might have is your water supplier adding more disinfectants (chlorine, chloramine) than normal. They will do this for a variety of reasons, as their main concern is supplying a safe product for human consumption. Unfortunately this isn't good for fish, especially if you are unaware of them doing this.

The product you're using to treat the water is a good one, converting the ammonia that comes from splitting chloramine into its components to ammonium, but perhaps your bio filtration is taking a bit of time to convert this from nitrite to nitrate, thus the spike.

The biggest problem is often getting the correct information from your water supplier as to when they plan on doing this, if they do plan it. The best thing you can do s learn about your water supply, and what they may do in certain instances, this is often weather or demand related. Once you figure this out you can adjust the amount of dechlorinator accordingly. I'll usually double dose my tanks, though at other times a regular dose is often more than enough.