Help please 🙏

[Sterling89]

Hi all,
I'm looking for some help/ideas/advice please.
I have a 180l tank which has been established for about 5 years. I took over the tank 2.5 years ago from my brother as he didn't have time to care for it properly with work, kids etc.
Did a partial water change yesterday lunchtime around 30% and removed a lot of algae from the glass. I use tap safe in the clean water as always. Rinsed filter pads and "hoovered" the gravel. Fed the fish at 8am today, all looked OK apart from one neon who was a bit pale. Between 10am and 1pm I have since lost said neon, 1 amano shrimp and 1 green barb. All lost colour and died pretty quickly after. Any ideas as to what may have caused this?
Water quality results were:
Ammonia 0, nitrate 10, nitrite 0, pH 6.4 and temperature is 26.9°c
Readings haven't really fluctuated since Feb last year
Nothing new has been added to the tank for at least 8 months and nothing removed that usually would be in there. Added a picture of the barb to show extent of colour loss.
Any thoughts would be really appreciated. Thanks guys

 

[Naughts]

Can you test for chlorine - the levels of chlorine in tank and water source? Sometimes the water companies add extra after working on the pipes and normal dechlorinator dosage won't be enough.
Did you temperature match the new water? Cold water shock can kill due to bubbles forming inside the fish.
How are the rest of the fish/ shrimp etc. ?

 

[Sterling89]

Haven't got anything to test chlorine in the water but will definitely invest.
Yeah, new water temp matched tank. I have a digital thermometer to test it. All other fish and shrimp look healthy and happy. Pleco has come up to top and banged the lid a couple of times today. He normally only does that if something is wrong, apart from not being able to test chlorine I can't find anything wrong

 

[Naughts]

Given the plecos behaviour, I would do another water change. Maybe add the maximum dose for dechloriantor on this occasion and again, carefully match the temperature.
Before this though, could the tank have been contaminated by the water change equipment? Maybe someone using a fish bucket for other cleaning for example?

 

[Sterling89]

It's only me who cleans the tank and rest of the house so I know the bucket hasn't been used for anything else and other cleaning bits are always wrapped up in a bag and stored in the bucket. I will try another partial water change, had attached picture of what I add to clean water. Maybe it's worth trying something different? Never had this problem before and always used this stuff before

 

[Naughts]

picture of what I add to clean water. Maybe it's worth trying something different?

Yes, get API tap water conditioner next time as is doesn't contain 'plant extracts' like aloe vera which can clog the fish's gills. It's OK to use the aquasafe up though, and it won't have caused the deaths. It was probably something in the water - you could phone the company and ask if they fixed any pipes (extra chlorine), changed the source (different parameters) or had flood water contaminants?

 

[Sterling89]

That's great thank you. I go for the API stuff next time. Aquasafe is pretty much gone now anyway. Good idea, will email the water company and see if they changed anything. Everyone looks happy and healthy today so will just closely monitor them for now