Water Conditioners & pH

API Proper pH 6.5

FreshwaterSoft-water fish

API Proper pH 6.5 is a buffering powder for tanks that need soft, acidic water — tetras, discus, angelfish and other Amazon species. One scoop per 38 litres sets the pH at 6.5 and holds it there, so you are not chasing a drifting reading with a liquid every few days. The same dose removes chlorine and detoxifies heavy metals, and it carries electrolytes that help reduce stress, which makes it a water-change conditioner as well as a buffer. It is a phosphate buffer and is not recommended for aquariums with live plants. The tub holds 240 g.

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Dosage calculator

Enter your aquarium volume and the calculator works out how much API Proper pH 6.5 to use for each rate on the pack.

Aquarium volume

Measured in

Use the water the tank actually holds, less substrate and decor.

Buffer dose1 scoops per 38 litres
Enter a volumeAt set-up and each water change; repeat if pH drifts more than 0.2

Very hard, strongly buffered tap water may need two doses to reach 6.5.

A guide only — always follow the dosing instructions printed on the pack, and measure with the bottle's cap or a syringe rather than by eye.

Technical details

Product type	Powder pH buffer and water conditioner
Sets pH at	6.5
Pack size	240 g
Dose	1 scoop per 38 litres; repeat when pH drifts more than 0.2
Also does	Removes chlorine, detoxifies heavy metals, adds electrolytes
Best for	Tetras, discus, angelfish and other soft-water species
Buffer type	Phosphate buffer
Safe with	Fish and invertebrates — not recommended with live plants
Suitable for	Freshwater aquariums
Made by	Mars Fishcare, USA

Phosphate buffers register as KH on a carbonate hardness test, so expect a higher KH reading after dosing.

Should I use Proper pH 6.5 or pH Down?

Use Proper pH 6.5 when you want the tank to stay at 6.5 without fuss — it buffers the water so the value holds between water changes, and it conditions the water at the same time. Use pH Down for a small one-off correction or in a planted tank, because Proper pH 6.5 is a phosphate buffer that binds the iron and trace elements plants need. The dose is one scoop per 38 litres; very hard tap water buffered above pH 8 may take two doses to overcome, and softening the water first makes the job easier.

Locks pH at 6.5 instead of nudging it

Proper pH is a buffer, not a one-off corrector. Once dosed it resists the upward drift that hard tap water causes, holding the water at 6.5 until the next water change. Retest after a few days; if the reading has moved by more than 0.2, repeat the dose. Very hard, strongly buffered tap water may take two doses to overcome its own buffering.

Conditions the water in the same scoop

Because the powder removes chlorine and detoxifies heavy metals, you do not need a separate dechlorinator when you use it for a water change. Added electrolytes help fish cope with the stress of new water and handling. Dose by the volume of new water you add, or the whole tank when setting it up.

For fish-only tanks, not planted ones

Proper pH 6.5 works as a phosphate buffer, and phosphate binds trace elements such as iron that plants need. API therefore advises against using it with live plants. It is safe with invertebrates. If your soft-water tank is planted, lower pH with pH Down instead, or soften the source water.

Harmless haze in hard water

In water with high general hardness the buffer can throw a temporary cloudiness as hardness minerals come out of solution. It is not harmful and normally settles within 24 – 48 hours; Accu-Clear speeds it along. To avoid it altogether, bring the hardness down to around 100 ppm before dosing.

Frequently asked questions

Do I still need a dechlorinator with Proper pH 6.5?

No. The powder removes chlorine and detoxifies heavy metals as it buffers, so one scoop per 38 litres of new water does both jobs at a water change.

Can I use Proper pH 6.5 in a planted aquarium?

API does not recommend it. It is a phosphate buffer, and phosphate ties up iron and other trace elements that live plants need, leading to deficiencies. Use pH Down in planted tanks instead.

Why did my KH reading jump after dosing?

KH test kits measure how strongly water resists acid, and a phosphate buffer resists it just as carbonate does, so the kit reports it as KH. The reading is real for buffering purposes but does not mean carbonate was added.

My water went cloudy after adding the powder — is that a problem?

No. In hard water some hardness minerals drop out of solution for a day or two; it is harmless and clears on its own, or faster with Accu-Clear. Softening the water to about 100 ppm first prevents it.

Is API Proper pH 6.5 available in South Africa?

Yes. The 240 g tub is available from Jungle Aquatics in Fourways, Johannesburg, with delivery to anywhere in South Africa; pricing and stock are on jungleaquatics.com.

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