Tap water in Pakistan: how do you make it safe for fish?

Most first tanks die of the water rather than the fish.

Tap water carries chlorine, or chloramine, and often both. They burn gills, and they also kill the bacteria in the filter that keep the tank alive — which is why a big water change can crash a tank that was fine the week before.

Here is the bit that catches people out. Standing water in an open bucket overnight lets chlorine gas off, and does nothing whatsoever to chloramine. If your supply is chloraminated, the bucket trick is not treatment, it is a delay. A dechlorinator handles both, instantly.

Which do you use? Does your area actually supply chlorine or chloramine — has anyone asked their water board? And if you are on tanker water, does that change what you do?

Dechlorinator, always. A bottle is about Rs 600 and it lasts a year for a small tank. It is the cheapest insurance in the hobby and people skip it to save six hundred rupees.

I did the bucket-overnight thing for a year and lost fish constantly and could not work out why. Switched to a conditioner and the problem just stopped.

Karachi, fifteen years, and this is the thing I answer most often, so let me do it properly.

Chlorine vs chloramine, and why it matters. Chlorine is a gas dissolved in water and it does leave if you stand water in an open bucket for 24 hours with a bit of surface movement. Chloramine is chlorine bonded to ammonia and it does not gas off at all — you can stand it for a week and it is still there. Worse, when a conditioner breaks the bond you are left with free ammonia, which is why some conditioners specifically say "removes chloramine" and cost a bit more. The cheap ones only handle chlorine.

I asked my water board and got nowhere, which I suspect is everyone's experience. So the practical answer is: assume chloramine and use a conditioner that handles both. It costs a couple of hundred rupees more per bottle and removes the entire question.

Tanker water is a different problem and a bigger one. Chlorine is often the least of it — you are getting unknown hardness, sometimes salinity, and occasionally water that has been sitting in a tank with things growing in it. What I do:

• Never fill a tank straight from a tanker delivery. Store it 48 hours first.
• Buy a TDS meter. About Rs 1,500 and it is the single most useful tool I own. My tanker water has ranged from 380 to over 900 TDS from the same supplier. If you had done a 50% water change on the day the 900 arrived you would have wiped out the tank, and you would have blamed the fish.
• If your area is on a mix of supply and tanker, test every time.

The bit that actually kills tanks, and it is not the chlorine. People do a big water change to "fix" a problem, dechlorinate correctly, and the tank still crashes. That is temperature and pH shock, not chemistry. New water within a couple of degrees of the tank, always. And never change more than 30% at once unless something is genuinely wrong.

Order of operations: conditioner into the bucket, stir, wait a minute, then into the tank. Not into the tank first and then hoping.

One thing nobody mentions: if you have an RO unit at home for drinking water, do NOT use pure RO water for a freshwater tank without remineralising it. It has nothing in it — no hardness, no buffer — and the pH will swing wildly. I have seen someone lose an entire tank of tetras this way while being very pleased about how pure their water was.

Short version for anyone who does not want to read all that: buy a conditioner that says chloramine, and buy a TDS meter if you are on tanker water. Those two things solve about 80% of first-tank deaths.

The TDS variation from the same tanker supplier is genuinely alarming and I am buying a meter today. I have lost fish after water changes twice and never understood why, because I was doing everything else right.

Six weeks with a TDS meter now. My supply water swings from 210 to 340 depending on the day of the week. I had no idea. Small water changes now, more often.