Aquario Neo Black

A liquid water conditioner built on the humic and fulvic acids abundant in natural blackwater, which lowers pH and tints the water.

Blackwater is the tea-coloured water of streams that run through fallen leaves and wood. The colour comes from tannins and from humic and fulvic acids leaching out of that plant matter, and the water is naturally acidic. pH is the acidity scale — below 7 is acidic, above 7 alkaline.

In Aquario's own words, it “contains humic acid and fulvic acid, which are abundant in black water, and trace elements that are beneficial to tropical fish and aquatic plants”, and “its safe ingredient slightly lowers the PH of the tank”. Aquario position it for South American species and planted tanks that prefer weakly acidic water, and note the degree of pH drop depends on the environment.

What that does in a tank: it moves water chemistry toward tannin-stained, acidic blackwater conditions. The water darkens noticeably at first and then lightens over time. Because it moves pH downward, the effect compounds with anything else already acidifying your tank — an active soil (a substrate that deliberately pulls pH down), or a media that strips minerals out of the water like Neo Bag Plus — so Aquario's instruction is to measure pH as you dose rather than assume.

Dosing: 10 ml per 40 L — note this is double the rate of several other bottles in the range, so don't dose it from muscle memory. Aquario say to increase the amount if you want a larger pH drop. The 300 ml cap holds 5 ml and the 1 L cap holds 10 ml. Shake before use.

• Humic and fulvic acids plus trace elements, as found in natural blackwater
• Aquario claims: slightly lowers pH; suited to species and planted tanks preferring weak acidity
• Dose 10 ml per 40 L — double the rate of much of the range · increase it for a larger pH drop
• Aquario's own instruction: measure pH while dosing, as the drop depends on your water
• Water darkens like blackwater at first, then gradually lightens — normal