Water Conditioner Fish Tank Guide: Chlorine and Chloramine

Singapore aquarists often lose fish to tap water they assume is “treated” — it is, but not the way cheap dechlorinators handle it. PUB treats water with chloramine, a bonded chlorine-ammonia compound that outperforms simple chlorine basic conditioners neutralise. This water conditioner fish tank guide from Gensou Aquascaping at 5 Everton Park explains why the bottle under your cabinet matters more than most hobbyists realise, and which products genuinely handle SG tap water. Getting this wrong is the silent killer behind first-month fish loss.

Chlorine vs Chloramine — The SG Difference

Free chlorine dissipates naturally from water left standing 24 hours. Chloramine does not — it is a stable chlorine-ammonia bond engineered to persist through distribution pipes. PUB switched to chloramine treatment decades ago for public health reasons. The consequence for aquarists: any conditioner that only neutralises chlorine leaves the ammonia portion toxic in your tank. Basic conditioners (Tetra AquaSafe basic, older formulas) handle chlorine but not chloramine’s ammonia release. Check the bottle — it must explicitly state “chloramine” in the ingredient claim.

How Chloramine Breaks Down

When a proper conditioner hits chloramine, two things happen: sodium thiosulfate (or equivalent) neutralises the chlorine portion, and an amine-binding agent temporarily detoxifies the released ammonia. The ammonia is not removed — it is held in a non-toxic bound state for 24-48 hours until biofilter bacteria convert it. This is why Seachem Prime ($45 for 500 ml at C328 Clementi) is the SG standard; it binds ammonia, nitrite and nitrate up to 1 ppm in addition to neutralising chloramine.

Seachem Prime — The SG Benchmark

Prime dechlorinates at 1 ml per 40 litres, binds up to 1 ppm ammonia/nitrite at the same dose, and emergency-doses up to 5x during ammonia spikes. A 500 ml bottle treats 20,000 litres — 2-3 years of water changes on a 150 L tank. Local pricing sits at $45 for 500 ml, $85 for 2 litres. For any SG hobbyist serious about livestock, Prime is not optional — it is the baseline.

API Stress Coat — The Slime Coat Claim

API Stress Coat ($35 for 473 ml at C328) adds aloe vera to the dechlorinator formula, claiming to replace fish slime coat during transport. Evidence for aloe benefits in freshwater fish is thin; the product does reliably neutralise chloramine. Stress Coat binds ammonia less aggressively than Prime, so doubles as a transport-day conditioner rather than daily water-change product. Pairs well with Prime rather than replacing it.

Fluval AquaPlus and Tetra AquaSafe

Fluval AquaPlus ($28 for 250 ml) handles chloramine and adds a slime-coat polymer. Performance matches Stress Coat at lower cost for smaller tanks. Tetra AquaSafe (current formulation, $24 for 250 ml) handles chloramine — the older AquaSafe bottles from pre-2015 did not, so check current labelling. Both are adequate for non-breeding community tanks where ammonia binding matters less than pure dechlorination.

Kordon NovAqua and Amquel Plus

Kordon’s two-bottle system (NovAqua dechlorinates, Amquel Plus binds ammonia/nitrite/nitrate) is a professional option costing more upfront ($95 for 1 litre of each) but dosing efficiently at 1 ml per 40 litres. Popular with breeders and shrimp keepers for precise detoxification. Less common at casual SG shops — order via Shopee or specialist importers.

DIY Sodium Thiosulfate

Pure sodium thiosulfate ($12 for 500 g Shopee) dechlorinates at 1 g per 100 litres for chlorine, but does nothing for chloramine ammonia. For SG water, DIY dechlor alone is inadequate. Large-scale pond keepers sometimes run DIY thiosulfate plus separate ammonia binder, saving on 500+ litre water changes. For tank-scale hobby use, branded conditioner is cheaper per litre once you factor in chloramine handling.

Dosing Accuracy

Most conditioner bottles come with cap measurements. Prime’s 5 ml cap treats 200 litres; eyeballing “half a cap” risks underdosing. A 1 ml pipette ($3 at Daiso) delivers precision for small tanks. Underdosing leaves residual chloramine; overdosing Prime is harmless up to 5x, but overdosing ammonia-binding products beyond recommendations can temporarily lower oxygen — aerate heavily during emergency doses.

When to Dose

Add conditioner to the new water before it enters the tank, not after. Dosing post-fill means chloramine contacts fish gills for the 10-30 seconds before mixing. For Python-style direct-fill setups, dose the full tank volume of conditioner into the tank before opening the Python valve. For bucket changes, dose and stir the bucket, then pour.

Beyond Dechlorination

Modern conditioners layer in extras: heavy metal binding (copper, lead, zinc from old HDB pipes), slime coat polymers, and mild ammonia/nitrite detox. For SG aquarists in older flats with aged copper plumbing, a product that binds heavy metals matters — long-term copper exposure kills invertebrates and stunts fish. Prime, AquaPlus and Stress Coat all handle this; older formula Tetra AquaSafe does not.

Singapore Sourcing Summary

Seachem Prime: $45 for 500 ml at C328 Clementi, $85 for 2 litres Shopee bundle deals. API Stress Coat: $35 for 473 ml at most LFS. Fluval AquaPlus: $28 for 250 ml at Green Chapter Jurong West. Tetra AquaSafe: $24 for 250 ml widely stocked. Kordon NovAqua + Amquel Plus: $95 each per litre Shopee specialist importer. Pure sodium thiosulfate: $12 for 500 g Shopee. For 90 per cent of SG tanks, Prime handles every water-change scenario — start there, add Stress Coat or AquaPlus as a transport-day backup.

Related Reading

• Fish Tank Dechlorinator Guide
• Seachem Prime Complete Guide
• Aquarium Water Parameters Singapore
• Fish Tank Water Change Guide Singapore
• Aquarium Ammonia Management