All fish dead after water change - advice needed.

54and56

Hi all,

I've a large 600 litre tank hosting +/- 35 Malawi cichlids and 3 rusty plecos which I've successfully maintained for over 10 years.

The tank has 2 X JBL 1502 external filters and a Tunze 6065 Turbelle Wavemaker to ensure good filtration and plenty of water flow / oxygen exchange.

Yesterday I did a 66% water change and filter clean out (rinsing filters and biological media in expelled tank water etc) in the usual manner and last night the tank looked great with all the fish looking well and active but this morning I just discovered all the Cichlids are dead. The Pleco's are still alive.

I'm devastated but need to figure out what caused the wipe out so looking for a little perspective from other fishkeepers.

My normal monthly routine is to do a 50% to 66% water change and rinse out one of the two filters so each filter gets cycled every two months.

When filling the tank back up I use API Stress Coat (5ml per 40L of water so 50ml used yesterday) to make the tap water safe but yesterday I also used Tetra EasyBalance (2.5ml per 10L of water so 100ml used yesterday) which I've used before but don't use every time.

The only other thing (which on reflection I'm thinking is in fact the cause) is I removed the sliding glass panels from the top of the tank which a family member cleaned in a bath as they'd become fairly discoloured. I didn't pay attention to the glass cleaning as I was busy with filter etc so when the glass panels came back clean I just slotted them back in.

Turns out the glass panels were sprayed with a Kitchen Cleaner disinfectant (see ingredients photo below), scrubbed and rinsed.

I'm thinking residue from the kitchen cleaner must have mixed in with the tank water as I filled the tank right up to the glass panels so their full surface was in contact with the water.

Two things I'm looking for assistance with:-

1. Am I correct to think it was most likely residue from the disinfectant which will have poisoned all the fish or could it be that I overdosed the tank by using both Stress Coat and Easy Balance at the same time?
2. How do I ensure whatever killed the fish is expelled from the tank? I'm assuming I'll need to do several 90% water changes over a period of a week or two before I can try introducing new stock?

Thanks in advance for your input.

Feeling totally stupid and gutted so please go easy on me!!

scwazrh

1. Am I correct to think it was most likely residue from the disinfectant which will have poisoned all the fish or could it be that I overdosed the tank by using both Stress Coat and Easy Balance at the same time?

Would agree with you that’s the cause.Would also say 66% and a filter rinse is too much at one time but you’ve probably been doing that for years and they were able for it.The disinfectant would have a pushed the balance over the edge this time.

Not a nice morning for you.Very disheartening to lose the full stock at one time ,particularly Malawi.

How do I ensure whatever killed the fish is expelled from the tank? I'm assuming I'll need to do several 90% water changes over a period of a week or two before I can try introducing new stock?

Empty the tank , rinse and dry and repeat many times .Also I’d bin the substrate and scrub the rocks.No harm replacing filter media and then add fish as if it’s a new setup.

54and56

Thanks @scwazrh, I think you're right unfortunately.

Not sure what I'll do with the Pleco's whilst I'm rehabbing the tank and to be honest right now I'm thinking maybe now is a good time to quit altogether and just get rid of the tank as I don't have the motivation to essentially start again.

I'm probably just a bit emotional right now and in a day or two practicality will be restored!!

redseat1

Oh wow, you must have been shocked. That's awful. I hope you rethink your decision to quit, after 10 years of care it would be a shame to allow one slip stop everything.

54and56

https://www.boards.ie/discussion/comment/122556527#Comment_122556527

Hi @redseat1, yes, after the initial disappointment and shock subsided I decided to carry on so did a few large water changes to flush out the cleaning agent toxins and used the remaining (hardy buck) Pleco's as canaries in the mine so to speak. When they were healthy after 72 hours I purchased 2 juvenile yellow lab cichlids and when they survived 48 hours I introduced another 4 cichlids.

Fast forward 2 weeks and I'm back up to a stock of 30 fish in total having purchased 4-6 (mostly) juvenile fish from different sources every few days and only introducing more if the newest fish had settled in well and the tank was looking good with good water readings etc.

redseat1

That looks like a fantastic set up.

Silverfish

Sorry for your losses, that's a horrible situation :(

I'd switch to using Seachem Prime for water detox - I also left a plastic 120L tub of water sit for 24 hours before using it to do a water change, just to ensure chlorine dissipation. I'd also switch to 20% water change weekly rather than larger quantity monthly, it's less stressful for the fish. Either way it didn't sound like the water changes were the issue, and it was almost definitely the cleaning products on the glass.

Nice set up and glad you decided to keep going, I lost my fish after moving house to a totally different water supply and even though I matched temps, hardness ph and kh, I still lost the lads, and quit after that! Once you quit it's harder to get going again so it's best to get back on the horse straight away.

54and56

Thanks @Silverfish

Is Sachem Prime an alternative to API Stresscoat? I think i used it in the past but switched to Stresscoat for some reason. Might just have been availability.

Alkers

Id say it was definitely the cleaner but I'd echo that your water change regime is too much at one time. I do 20% water change every 7-10 days with my Malawi and I only clean a filter every three months (have two for redundancy).

Malawi are such breeders, you could likely have repopulated for free from others, if you ever need any let me know

54and56

https://www.boards.ie/discussion/comment/122560699#Comment_122560699

Thanks @alkers, appreciate that.

My usual routine was to do a 66% water change every 3 months and just top up evaporated water every few weeks. Worked fine (very few fish losses) for years but I also know it's not optimum for breeding etc. I had a few fry produced over the years but not many. I'm a low maintenance (lazy) fish keeper to be honest.

With this new batch I'll ditch the 3 month 66% routine and adopt a more orthodox water change cycle.

Alkers

Yeah, you just need to get into the habit of it and establish a routine!

Silverfish

https://www.boards.ie/discussion/comment/122560648#Comment_122560648

Yeah - it's much better imo as you use less and while it removes chlorine and chloramines, same as stresscoat, you use less per L and it's just more effective. There's also special marine grade glass cleaner you can get - Zlements I think - that'll help in the future!

Alkers

Also just thinking, if all your ornaments are plastic - you should pick up some live rock. It stacks nicely and makes so many hiding places for smaller fish, as well as hardening the water which is more like the Malawi environment.

54and56

Thanks @Alkers, I do have 4-5 pieces of natural rock and also some bog oak. There are some plastic decorations but not too many, just for a bit of colour and movement.

Nice mature looking tank by the way.