Water changes are where careful shrimp keepers accidentally kill their shrimp. Not by doing too few — by doing them too big, too fast, or with water that doesn't match what's already in the tank. A shrimp tank wants small, regular, gentle changes, and the difference between that and the well-meaning half-tank refresh is the difference between a steady colony and a bad moulting season. Here's how much to change, how often, and the safe way to do it.
How much, and how often
For a stable, mature shrimp tank, we change 10–20% of the water each week. That's it — a modest weekly change, kept to a rhythm.
Small and regular beats large and occasional every time, and the reason sits at the heart of shrimp keeping: every water change is a small disturbance to the tank's chemistry, and a big change is a big disturbance. Swap 15% and the tank barely notices. Swap half and you've shifted the TDS, the temperature and potentially the pH all at once, which reads to a shrimp as a sudden environmental jolt. A steady 10–20% a week keeps nitrate down and minerals topped up without ever handing the colony one of those jolts.
There's a bit of judgement in where you land inside that band. A lightly stocked, heavily planted tank ticking over nicely might only need 10%. A busier colony, or a newer tank still finding its feet, does better nearer 20%. What you're managing is nitrate — keeping it under 20ppm — and the general freshness of the water, both of which a weekly 10–20% handles comfortably in most tanks. The full target picture for every parameter is in our Neocaridina water parameters guide.
Why a big water change is dangerous
It feels counterintuitive. Fresh water is good, so more fresh water should be better — and for many fish, a big change is a fine idea. Shrimp are not fish.
The danger is the swing, not the water. When you replace a large fraction of the tank at once, the new water's TDS, temperature and pH are almost never a perfect match for what's leaving, so the whole tank lurches towards the new values in one step. That sudden shift is the classic trigger for a bad moult. A shrimp part-way through building or shedding a shell, hit with a chemistry change it didn't expect, is the exact scenario behind the white ring of death — the failed moult where the shell separates but the shrimp can't pull free. Most don't survive it.
The mineral side matters just as much. Shrimp harden their new shells from the calcium and magnesium in the water, and a big mismatched change can send GH lurching in either direction at the worst possible moment; the mechanics are laid out in failed moults and the GH connection. This is why "I did a big water change to help them and they started dying" is such a common and heartbreaking story. The tank didn't need rescuing. It needed leaving mostly alone.
The safe method, step by step
None of this is difficult once the habits are in. The whole job is preparing the new water properly and adding it gently.
Prepare the new water first. Draw your replacement water and treat it before it goes anywhere near the tank. Dechlorinate it — every time, with a conditioner rated for chloramine as well as chlorine, since much of the UK supply carries chloramine that won't gas off on its own. Our notes on choosing a shrimp-safe dechlorinator cover what to look for. If you're in a soft-water area, remineralise the new water to your usual TDS at this stage too, so it matches the tank rather than diluting its minerals; the method is in remineralising RO and rainwater.
Match the temperature. Cold tap water in a British winter can be startlingly cold, and a slug of it into a warm tank is a temperature swing in its own right. Get the new water close to tank temperature before it goes in — a few minutes' attention that removes one of the biggest avoidable shocks.
Remove the old water gently. Siphon out your 10–20% slowly, using the opportunity to lift debris from open substrate, but keeping well clear of any spot where shrimplets shelter. A pre-filter sponge or a stocking over the siphon end stops a stray baby disappearing up the tube.
Add the new water slowly. Pour it back in over a surface — a plate, a bag, your hand — so it trickles rather than dumps, and take your time. Slow is the whole point. The tank should absorb the change without the shrimp registering that anything happened.
The drip water change
For a soft-water tank, a colony recovering from trouble, or simply keepers who like a belt-and-braces approach, there's a gentler version still: the drip water change. Instead of pouring the fresh water back, you run it in through a siphoned airline with a knot loosely tied in it, exactly as you would when drip acclimatising new arrivals — a slow, steady trickle over a good stretch of time rather than a top-up in one go.
It takes longer and it's rarely necessary in a settled tank on a modest weekly change, but it's the safest way to introduce water there is, because the tank's parameters move so gradually that nothing gets a shock. When the margins are tight — very soft water, valuable stock, a colony you're nursing — it's a technique worth having in your back pocket.
Topping up is not a water change
One habit that quietly saves colonies: keep the tank topped up between changes, and don't confuse topping up with changing.
Water evaporates; minerals don't. So as the level drops, the minerals left behind concentrate and the TDS creeps upward — a slow drift that becomes a swing the day you finally notice the low level and refill in one go. Top up little and often with dechlorinated water to hold the level steady, and the TDS stays put. Watching that number is the cheapest early warning in the hobby, as we set out in the TDS guide for shrimp keepers.
The key distinction: a top-up replaces evaporated water, which left its minerals behind, so plain dechlorinated water is right for it. A water change removes mineral-laden tank water, so its replacement should be remineralised to match if you're in a soft-water area. Muddle the two and you'll slowly drift your parameters without meaning to.
When to change more, or less
The 10–20% weekly rhythm suits most established tanks, but a few situations call for a tweak.
A brand-new tank, or one recovering from an ammonia or nitrite reading, benefits from more frequent small changes to keep the water clean while it stabilises — several gentle changes across a week rather than one bigger one. A heavily stocked colony, or one you're feeding hard to push breeding, may need to sit at the top of the band. Conversely, a lightly stocked, densely planted tank with plants mopping up nitrate can genuinely coast on 10% or even a touch less, provided the tests stay clean.
The one rule that never changes is how you do it, not how much: small, temperature-matched, dechlorinated, added slowly. Even an emergency — a spiking parameter, a pollutant scare — is handled with a run of careful changes rather than one dramatic flush, because a big correction is itself a swing. Fold the weekly change into the rest of your upkeep with our 15-minute maintenance routine, and the whole thing becomes a habit you barely think about, tied into the wider cherry shrimp care guide.
FAQ
How often should I do a water change in a shrimp tank?
Once a week suits most tanks. A small, regular change — 10–20% weekly — keeps nitrate down and minerals topped up without ever giving the colony a jolt. A settled, planted, lightly stocked tank can stretch to fortnightly on a small change if the tests stay clean, while a new or heavily stocked tank does better with a weekly change, or several small ones, until it stabilises.
How much water should I change in a shrimp tank?
10–20% at a time is the sweet spot. Small and regular beats large and occasional, because every change shifts the tank's chemistry a little, and a big change shifts it a lot. Swapping half the tank at once moves TDS, temperature and pH together, which is the kind of swing that triggers failed moults. Keep changes modest and the colony never feels them.
Can a water change shock or kill shrimp?
Yes, and it's a common way to lose them. The danger is a sudden change in temperature, TDS or pH when you swap too much water at once or add water that doesn't match the tank. That swing can trigger a fatal failed moult. Prevent it by keeping changes to 10–20%, matching the new water's temperature, dechlorinating it, remineralising if you're in a soft-water area, and adding it slowly.
What is a drip water change for shrimp?
It's the gentlest way to add new water: instead of pouring it in, you run it through a siphoned airline knotted to a slow trickle, the same method used to acclimatise new shrimp. The tank's parameters shift so gradually that nothing gets a shock. It's more effort than a normal change and rarely needed in a settled tank, but it's invaluable for soft-water tanks, valuable stock, or a colony you're nursing back to health.
Do I need to dechlorinate water for every water change?
Every time, without exception. UK tap water carries chlorine or chloramine, both of which harm shrimp, and chloramine won't gas off if you leave the water standing overnight the way plain chlorine once did. Treat every batch of new water with a conditioner rated for chloramine before it goes in — for a top-up as much as a full change. It's the one step in the whole routine you never outgrow.