How to Raise GH Naturally in Soft Water Aquariums
Singapore’s PUB tap water is naturally soft, typically measuring GH 2-4 out of the tap. While many tropical fish tolerate this, species that need harder water and shrimp that require minerals for healthy moulting often struggle. Knowing how to raise GH naturally in a soft water aquarium is an essential skill for local hobbyists. This guide from Gensou Aquascaping at 5 Everton Park, Singapore, covers proven methods drawn from over 20 years of hands-on experience.
Why GH Matters
General hardness measures dissolved calcium and magnesium in your water. These minerals serve critical biological functions: calcium strengthens bones, shells, and exoskeletons, while magnesium supports enzyme activity and muscle function. Shrimp are especially vulnerable to low GH; insufficient minerals lead to failed moults, the leading cause of death in Neocaridina and Caridina colonies. Fish from hard-water habitats, such as livebearers and African cichlids, also exhibit poor health and reduced breeding in excessively soft water.
Crushed Coral and Coral Sand
Crushed coral is one of the most accessible and reliable GH boosters. Place it in a mesh bag inside your filter or scatter a thin layer beneath your main substrate. As water flows over the coral, it slowly dissolves calcium carbonate, raising both GH and KH simultaneously. The rate of dissolution increases in acidic water and slows as pH rises, creating a self-regulating effect.
Start with a small amount, roughly 50-100 grams per 50 litres, and test GH weekly. Adjust quantity based on your target range. Crushed coral is inexpensive at about $3-5 per kilogram from local aquarium shops.
Seiryu Stone and Limestone
Certain aquascaping rocks naturally leach minerals. Seiryu stone, a popular choice in Iwagumi layouts, gradually raises GH and KH over time. Limestone and Texas holey rock have a similar effect. If you want harder water and an attractive hardscape, these rocks serve double duty. Test your water parameters over the first few weeks after adding mineral-rich rocks to gauge their impact.
Cuttlebone for Calcium
A piece of cuttlebone, available from any pet shop for under $2, provides a slow-release calcium source. Snails and shrimp will rasp directly on its surface, supplementing their mineral intake. Cuttlebone raises GH without significantly affecting KH, which is useful when you want harder water but prefer to keep carbonate hardness low. Break it into smaller pieces and wedge it behind driftwood or rocks to keep it from floating.
Commercial GH Remineralisers
For precise control, commercial products like Salty Shrimp GH/KH+ or Seachem Equilibrium let you dose exact amounts during water changes. Dissolve the powder in your replacement water before adding it to the tank. This method is especially popular among shrimp breeders who need consistent TDS readings. A single tub costs $15-30 on Shopee or Lazada and lasts months for a typical nano setup.
When using remineralisers with RO water, you control GH independently of other parameters, a significant advantage for species with narrow tolerance ranges.
Eggshells and DIY Mineral Packs
Cleaned, crushed eggshells work as a free calcium supplement. Bake them at 100 °C for 20 minutes to sterilise, then crush into small fragments and place in a filter bag. The effect is gentler and slower than crushed coral, making eggshells suitable for minor GH adjustments in nano tanks. Combine with Epsom salt (magnesium sulphate) at about one teaspoon per 40 litres to raise magnesium alongside calcium for a more balanced mineral profile.
Monitoring and Adjusting
Test GH with a liquid drop test kit rather than strips for accuracy. Strips are convenient but often give unreliable readings in the lower GH ranges common in Singapore. API and JBL drop kits cost around $10-15 and provide dozens of tests. Measure weekly when first adjusting parameters, then monthly once stable.
Raise GH gradually, no more than 1-2 degrees per day, to avoid shocking sensitive livestock. Sudden mineral spikes can stress fish and trigger emergency moults in shrimp.
Matching GH to Your Livestock
Neocaridina shrimp thrive at GH 6-8. Caridina species prefer GH 4-6 in buffered soft water. Livebearers like guppies and mollies do best at GH 8-12. African cichlids may need GH 10-20. Know your target before you start adjusting, and choose the method that gives you the right amount of control. Gensou Aquascaping Singapore can help you test your water and recommend the most practical approach for your specific tank and inhabitants.
Related Reading
emilynakatani
Still Have Questions About Your Tank?
Drop by Gensou Aquascaping — most walk-in questions get answered in under 10 minutes by someone who has set up hundreds of tanks.
5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
