Aquario Neo Bag Plus

A mesh filter bag that adsorbs positive-ion (cationic) components — calcium and magnesium — and which Aquario says lowers pH toward weakly acidic water.

To adsorb is to make something stick to a surface: the media pulls minerals out of the water and holds onto them, rather than adding anything in. pH is the acidity scale — below 7 is acidic, above 7 is alkaline. Calcium and magnesium are the two minerals that make water “hard”.

In Aquario's own words, Neo Bag Plus “chemically adsorbs positive ion(cationic) components such as calcium and magnesium” and “quickly lowers pH to maintain weak acidity water quality”. Note the name: the “Plus” refers to the charge of the ions removed, not to raising pH or hardness. This bag brings both down.

Inside are white and black “energy balls” which Aquario says supply organic carbon and trace elements — the minerals living things need in tiny amounts — supporting the bacteria that biologically remove nitrogen compounds and pollutants.

What that does in a tank: stripping calcium and magnesium lowers general hardness — often written GH, a measure of how much dissolved calcium and magnesium the water carries — and Aquario claims pH follows it down. How far and how fast depends on your source water and how much media you run against your volume. Aquario's own instructions say to watch pH and stop using it if the reading falls too low — worth heeding, because the effect stacks with anything else acidifying the tank, such as an active soil (a substrate — the material covering the tank floor — that deliberately pulls pH down).

Aquario position the bag for freshwater fish and plants that prefer soft, slightly acidic water, and specifically except African cichlids.

• Adsorbs cations — calcium and magnesium — lowering general hardness; Aquario also claim it lowers pH
• White and black energy balls supply organic carbon and trace elements for the bacterial colony
• Aquario dosing: 1 bag per 60 L, or an extra bag if you want a quicker effect. 8 bags per pack, each 12 × 8 cm
• Before use, Aquario say to shake it in clean water about 20 times; black water coming out is normal and comes from the black energy ball
• Aquario say the energy ball slowly disappears after a month or two
• Aquario's own instruction: monitor pH and discontinue if it drops too low