pH up/down

Performance & sizing

Core numbers for matching this unit to your tank and electrical plan.

Power

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Flow rate

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Noise

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Dimensions

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Price range

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Tank fit (L)

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Consumables & maintenance

Follow the manufacturer schedule for seals, impellers, media, and other consumables.

Description

The number on the bottle matters less than the rate at which you move it, and moving it with acid has a specific trap in it. FAO's aquaponics manual describes that trap exactly. You add acid and at first nothing happens, because the acid is reacting with the buffers in the water rather than with the pH. So more goes in, still with no reading to show for it, until the buffers are used up and the pH drops sharply, which the manual calls a terrible and stressful shock to the system. Its way around this is not a smaller dose but a different order of operations: treat a reservoir of replacement water with the acid, check the pH there, and add the treated water to the system. FAO also names what gets used. Phosphoric acid is the mild one, though overusing it builds phosphorus up to toxic concentrations. Sulphuric acid is for extremely hard, basic source water, and the manual does not recommend it to beginners. Citric acid is singled out to avoid, because it is antimicrobial and can kill the bacteria in the biofilter. Going the other way, potassium hydroxide and calcium hydroxide are strong bases that need the same care as acids, while calcium or potassium carbonate is the safer route and raises KH and pH together. What is actually inside a retail bottle labelled pH Up or pH Down is not something this catalog has verified. Merck's aquarium chapter supplies the reason all of this has to be slow. Where a tank's pH falls gradually the fish adapt, often with no outward sign of distress; where it falls fast, the manual says the result could be death for the resident fish. Its correction for a tank that has drifted is daily small water changes, chosen to avoid pH shock and the ammonia toxicosis that arrives as the pH climbs back.

Sources

• merckvetmanual.com — https://www.merckvetmanual.com/exotic-and-laboratory-animals/aquarium-fish/management-of-aquarium-fish
• openknowledge.fao.org — https://openknowledge.fao.org/items/e4d11efd-d97a-4959-8ae2-8b7d3fd32c5e

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