StabHi Organic Substrate are pebbles that has been tested to stabilize the pH while biological nitrification processes continue.

Used StabHi to increase the pH, alkalinity and hardness of aquaria and fish ponds all at the same time. The biological processes in aquaria and fish ponds need the correct levels for pH and alkalinity to function properly. Equally important is to maintain the hardness by adding calcium and magnesium ions.


StabHi does all that in very much the same way as oyster shells do, and like oyster shells will finally, if enough volume and time is given, buffer the water at pH 8.27 (at atmospheric pressure CO2) Click to see experimental data.

Since koi keepers want to stabilise the pH of their pond at 7.0 – 7.2, it is necessary for keep enough StabHi available to “satisfy” the “acid creep”

Factors that will effect its dosage:

  • Flow rate: More effective mixing.

  • Total surface area available

  • Protein fed in the diet: Protein in the diet results in ammonia in the blood and subsequently in the pond water. Ammonia is oxidised in the nitrification process to nitrites and further into nitrates with the liberation of three hydrogen ions for each ammonia resulting in a higher hydrogen ion concentration (lower pH)

  • Carbon dioxide, CO2 concentration. The CO2 concentration of the water effects the pH and solubility of carbonates due to the carbonate/bicarbonate equilibrium.

  • Water temperature: The higher temperature will the solubility and reaction. The temperature effects the CO2 solubility and subsequently the pH

  • Constituents of the natural waters and the prevailing water parameters

  • Hardness will increase to the point where it has a negative impact on the water. Keep hardness below 120 mg/l as CaCO3 with flushing/backwashing.

  • Sunlight and algae will effect the pH via the diurnal variations in O2/CO2 concentrations due to transpiration/respiration.

  • Level of leaching of the pond. Poorly constructed and/or sealed concrete ponds will leach out in the absence of suitable alkalinity sources (eg StabHi, oyster shells, “bicarb” etc.

It can be seen that the interaction of the many factors make it very difficult to predict the precise dosage.

We therefore suggest to start with 5 x 4kg bags per 10-20 kl pond. If the pH increases beyond 7.2 reduce the volume of StabHi, but if it drops, increase the volume.

Always keep the hardness below 120mg/l of CaCO3, this will also keep the ionic content in check. The conductance of the water is a measure of the total ionic species and therefore a measure of the TDS (total dissolved solids) and visa versa.

 Increase the pH of a live ecosystem slowly over several days if the change will be more than 1 pH unit. (I personally do not believe for a koi pond it makes any different weather adjusting slow or fast . Get to your target value as quickly as possible and the fish will thrive. Of cause taking due consideration with diluting process.)

The pH scale is logarithmic, so exponentially less will be required as we approach the target value.

(Please keep record about you are doing, In such a way we understand what we are doing better)

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