Every water change on a shrimp tank should start with the same small step: treating the new water so it can't poison the colony. UK mains water is dosed with chlorine, and increasingly with chloramine, to keep it safe for people to drink. Both are toxic to shrimp, and the good news is that a bottle of water conditioner deals with them in seconds. The better news is that you don't need an expensive or clever one — you need the right basic one, used every single time.
Why UK tap water has to be treated
Water companies disinfect the mains supply so it reaches your tap free of anything that would make you ill. That's exactly what you want from drinking water and exactly what your shrimp can't cope with. Chlorine and chloramine are there to kill microorganisms, and a shrimp is a great deal more delicate than the bacteria they're aimed at.
Shrimp feel it faster than fish do. They're small, they breathe across a large gill surface for their size, and they have no reserve to fall back on when the water turns hostile. Chlorine burns gill tissue and disrupts the biofilm and beneficial bacteria the tank runs on. An unconditioned water change is one of the most common ways a healthy colony gets wiped out in an afternoon, and it sits near the top of our list in why are my cherry shrimp dying.
This applies wherever you live. Hard-water regions like London and the South East have tap water that's otherwise fine for cherries straight from the tap, as we cover in the UK tap water guide — but "fine for minerals" is not the same as "safe to pour in". Every mains supply in the country is disinfected, so every mains water change needs conditioning first, hard water and soft water alike.
Chlorine versus chloramine: why standing water isn't enough
For years the old advice was to fill a bucket, leave it out overnight, and let the chlorine gas off before you used it. That advice is half right, and the half that's wrong will kill shrimp.
Plain chlorine is volatile. Left standing, especially with a bit of surface movement or an airstone, it does slowly escape into the air over a day or so. If chlorine were the only thing in your water, patience would eventually do the job.
The problem is chloramine. Water companies increasingly use it because it's chlorine bonded to ammonia, and that bond makes it deliberately stable — it's designed to stay active all the way through miles of pipework to the far end of the network. Being stable is the whole point of it, which means it will not meaningfully gas off if you leave a bucket standing overnight, or over a week. You usually can't tell by looking whether your supply carries chlorine or chloramine, and it can change through the year; your water company will tell you if you ask. Because you can't rely on standing water and can't easily know which you've got, the safe habit is simple: treat every batch with a conditioner rated for chloramine.
| Chlorine | Chloramine | |
|---|---|---|
| What it is | A disinfectant gas dissolved in water | Chlorine chemically bonded to ammonia |
| Gases off if left to stand? | Slowly, over a day or more | No — it's built to stay stable |
| What neutralises it | Any dechlorinator | A conditioner that also handles chloramine and the released ammonia |
That last row is the one that matters when you're standing in the aquatics aisle.
What to look for in a shrimp-safe conditioner
The market is full of bottles making a lot of claims. Strip the marketing away and a shrimp-safe conditioner comes down to a short checklist.
It treats chloramine, not just chlorine. This is the non-negotiable one. A cheap "dechlorinator" that only tackles chlorine will, faced with chloramine, leave you worse off — it can break the bond and free the ammonia without dealing with it. A proper conditioner neutralises the chlorine, splits the chloramine, and detoxifies the ammonia that releases. The label will say it handles chlorine, chloramine and ammonia; if it only mentions chlorine, put it back. Freed ammonia is no small thing in a shrimp tank, as the ammonia, nitrite and nitrate guide explains — shrimp have no tolerance for it at all.
The dose per litre is sensible. Most conditioners are concentrated, so a small measured dose treats a whole bucket. That's good value, but it cuts both ways on a nano tank: a few millilitres too many is easy when the correct dose is a handful of drops. Measure it, don't eyeball it, and follow the dose-per-litre on the bottle for the volume of new water you're adding. There's no shrimp-specific dose — the standard fish dose neutralises the same chlorine and chloramine either way.
It doesn't come loaded with extras you don't need. Plenty of conditioners bundle in "slime coat" additives, aloe, stress-reducing polymers or colour tints. Those are aimed at fish skin and do nothing useful for an animal wearing a hard shell. None of it is necessary for shrimp, and some keepers prefer to keep those additives out of an invertebrate tank on principle. A plain conditioner that does the three core jobs — chlorine, chloramine, ammonia — is all a shrimp tank has ever needed.
A heavy-metal binder is a small bonus, not a requirement. Some conditioners also detoxify trace heavy metals, which is a mild plus given how sensitive shrimp are to copper. Treat it as a nice-to-have. It won't rescue a tank with a real copper source in it — that's a different problem entirely, covered in copper and shrimp — so don't buy a conditioner expecting it to fix contamination.
How to actually use it
The practical routine is short. Treat the new water before it goes anywhere near the tank: dose a bucket of fresh tap water for its volume, give it a stir, and it's safe within seconds to a minute. Temperature-match it to the tank and add it slowly, which matters as much as the conditioning itself — the mechanics are in our guide to safe water changes.
Some keepers dose the tank directly for the volume of water they're about to add, then pour the treated tap water in. That works too, though pre-treating the bucket is tidier and means the raw water never touches the shrimp. Either way, the rule that saves colonies is boring consistency: condition every change, every top-up, every time, including the one you're tempted to skip because you're only adding a litre.
Do you actually need a dechlorinator for shrimp?
If your water comes from the mains, yes — essentially always. There's no version of "just this once" that's safe, because you can't see chlorine and you often can't know whether chloramine is present. Even the hard London tap water that's otherwise ideal for cherries still arrives disinfected and still has to be treated.
The exceptions prove the rule. RO water has already had chlorine and chloramine stripped out by the filter, so it doesn't need dechlorinating — but it needs remineralising instead before it's fit for shrimp, which is a whole job of its own in remineralising RO and rainwater. Rainwater and well water carry their own risks rather than chlorine. For everyone else, on normal mains supply, a conditioner is simply part of the kit, as basic and non-optional as the tank itself — it's the first rule in our cherry shrimp care guide for good reason.
One bottle lasts a long time. Because the dose is tiny, even a small bottle sees a nano tank through many months of water changes, which makes it one of the cheapest pieces of insurance in the hobby.
FAQ
Do I need a dechlorinator for shrimp?
If you use mains tap water, yes, every time. UK supplies are disinfected with chlorine and often chloramine, both of which are toxic to shrimp — more so than to fish. There's no safe exception, even in hard-water areas where the tap water is otherwise fine for cherries. The only water that doesn't need dechlorinating is RO water, which has had chlorine removed already but needs remineralising before use instead.
Can I just let tap water stand overnight for shrimp?
Not reliably. Plain chlorine does slowly gas off from standing water over a day or more, but chloramine — which many UK water companies now use — is chemically stable and won't leave the water on its own, however long you wait. Since you often can't tell which your supply carries, standing water is a gamble with a colony's life. A conditioner rated for chloramine takes seconds and removes the guesswork.
What's the difference between chlorine and chloramine?
Chlorine is a disinfectant gas dissolved in the water; chloramine is chlorine bonded to ammonia to make it last longer in the pipes. The practical difference for shrimp keepers is stability: chlorine escapes from standing water eventually, chloramine doesn't. Chloramine also releases ammonia when it's broken down, so you want a conditioner that neutralises the chlorine, the chloramine and the ammonia together.
Is normal fish water conditioner safe for shrimp?
Usually yes, as long as it treats chloramine and ammonia rather than chlorine alone. The chemistry that neutralises chlorine for fish works identically for shrimp. The only things worth avoiding are the "extras" some conditioners add — slime-coat agents, aloe, colourants — which do nothing for a shelled animal. A plain conditioner covering chlorine, chloramine and ammonia is ideal, and the standard dose is the same.
How much water conditioner should I use in a shrimp tank?
Follow the dose-per-litre printed on the bottle for the volume of new water you're adding, not the whole tank's volume. Conditioners are concentrated, so on a small tank the correct dose can be just a few drops — measure it rather than guessing, since it's easy to overdo on a nano tank. There's no separate shrimp dose; the standard amount neutralises the same chlorine and chloramine.