Chlorine Remover Not Working

Hi, I have been having problems with high chlorine levels in my tank despite putting chlorine and chloramine remover.

About two weeks ago, I found one of my cherry barbs dead. It had been thin and struggling to swim before it died. At the time I assumed that it had died of old age but one of my other barbs is also struggling to swim. It keeps lying on the bottom of my tank and when it swims it is very floppy. Its gills are red. When I tested the water I got a chorine reading of 3.0 mg/l. 

I put more chorine remover into my tank which  hasn't lowered my chorine reading but the fish got better for a few days. The fish then started showing the same symptoms again. None of my other fish and shrimps are having problems.

I decided to do a water change yesterday with tap water treated with chlorine remover and ammonia remover but I am still getting the same chlorine reading of 3.0 mg/l. This is my normal procedure when I change the water and until now it has removed the chlorine from the water.  I have not made any other changes to my tank. The water change did not help the ill fish.

Since I started having problems I have tried 3 types of chlorine remover including 2 type that I often use and they are not working.

What  could be going wrong and what should I do next?

Thanks

Colin

Tank parameters:

Time set up: 5 years.
Volume: 47l
Filtration: Under gravel filter powered by an air pump
N0₃: 0
N0₂: 0
Temperature 24.3c
Ammonia: 0
Stock: 4 cherry barbs 3 other barbs 4  shrimps

Strange, normally chlorine would gas out of tap water within 8 hours (I let mine stand for 24 hours to make sure). 

Thanks for the replies everyone. My test kit  was not working. I hadn't realised it was two years out of date. I bought a new test kit (Tetra 6 in 1 test strip) and it gave a chlorine reading of 0

My barb died. When I found it  dead this morning its colourings were very pale and its gills were red. My other fish and shrimps are not having any problems. What might have been wrong with the barb that died?

How are you measuring the chlorine - and the other parameters?

I measured all the parameters with my old Tetra 6 in 1 test strip except the ammonia which was taken using a test tube test kit.

Which dechlorinators have you tried? With some brands you are not supposed to overdose, but others are OK.

My main ones are King British Safe Water and Interpet Bioactive Tapsafe. I only use one at a time. Which one I use depends on which shop I buy my dechlorinator from. I am normally careful about getting the right amount of tap safe but since I thought my tank had chlorine in it, I felt there was more risk to the fish from the chlorine than from using too much dechlorinator.

One thing that does concern me is your nitrate reading. It is almost impossible to have a reading of zero in a tank unless it is planted like a jungle, which is not really a good idea with a UG filter as the roots clog it up. What kind of tester are you using for that?

My old test kit was also giving a wrong nitrate reading. Todays test with the new kit gave me:
Nitrate  25 mg/l
Nitrite  0 mg/l
Chlorine 0 mg/l
My tank has a lot of java moss but no other plants

I hadn't realised that test kits expire but I am relieved that my tank water is not filled with chlorine. My remaining fish and shrimps are still ok.

How long since you got the fish that have died?

The cherry barb that died had been the tank for about a year. The other barb has been in the tank since February or March this year.

What species are the non-cherry barbs?

I think they are pentazona barbs.

Has there ever been any ammonia and/or nitrite in the tank while they were in there?

Not that I am aware of. I normally only test my water when I have problems.

Have you got any new fish recently?

No

Any other symptoms besides going thin and having red gills? The pale colour of the second death could have happened post mortem.

The second fish was swimming abnormally. It seemed very floppy when it was swimming but it seemed a normal weight when it died. The cherry barb was swimming normally before it died but was very thin.

Just to rule it out, have you ever seen any of the fish doing clear stringy poo? Or seen any red threads coming from the anus when the fish stop swimming for the odd second or two?

No I haven't seen either of these symptoms.

Are all the other fish still fit and healthy?

Other fish are still OK. They are swimming normally and are not gasping for air.

In that case, all I can suggest is to keep a close eye on the fish for a short while. Hopefully the two deaths were just "one of those things".

I hope so too. I will monitor them closely.