Water Hyssop

About

The thick-leaved, stiff, light-green Bacopa that a beginner genuinely cannot kill. Small obovate leaves 1-2.5 cm long sit in close pairs on an upright stem, and both leaves and stem are noticeably fleshy, almost succulent - that texture is the fastest way to identify it on a shop shelf. It is also the reason to plant it gently: the leaves are brittle and snap off if you push a bunch in by the foliage, so grip the bare lower stem with tweezers. Happy, it climbs straight up at an unhurried pace, keeps every leaf from substrate to tip, and on reaching the surface at 25-50 cm it converts to an emersed shoot and flowers white to pale mauve rather than stalling. There is no red form and no conditional colour: it is light green at 30 PAR and light green at 100, so for once the catalogue photo is honest. Light is the contested number here. Shops rate it medium and Tropica rates the 'Compact' cultivar low, but Flowgrow says medium to high, Aquarium-Guide says medium to very high, and Buce Plant says moderate to high - we set the floor at the demanding end, because the damage weak light does cannot be undone from the top. Too little light kills it and it gives no warning: it does not melt. The top stays perfectly green while the base of the stem rots away, until the plant detaches and floats up; a dense untrimmed bush does the same to its own lower stems by shading them. The fix is to replant the healthy top, not to dose more fertiliser. Starvation, meanwhile, shows nothing at all: no yellowing, no pinholes, just growth that stops. Judge this plant by how much new stem it makes in a week, not by how it looks. Growth rate is contested too - Flowgrow and Aquasabi's spec card say medium, while Aquarium-Guide, Buce Plant and Aquasabi's own prose say slow. We follow slow, which means it will not fill a background quickly and is a weak competitor against algae in a young tank. Next to it sits Bacopa australis under a near-identical Latin label - squeeze a leaf to separate them: thick and fleshy is monnieri, thin and papery is australis, which also grows fast, sprawls loosely and survives down to 4 C. Bacopa caroliniana smells of lemon when a leaf is crushed; monnieri is scentless, and that is the whole test. The 'crenata' printed on some listings is a retailer lumping several plants under one label, not the real Bacopa crenata, which is a demanding African species wanting high light, soft water and CO2. Stock sold around 2010 also went out labelled Hedyotis salzmannii, which is a genuinely different plant rather than a synonym. The 'Compact' cultivar is this same species bred short and bushy for the midground, but without CO2 and strong light it loses the compact habit and grows like ordinary Bacopa.

Care

Give it real medium light, roughly 30-80 PAR or 0.5 W/L and up, because weak light rots the base rather than the tips and no amount of fertiliser reverses it. CO2 is optional. Feeding is undemanding but not nothing - Flowgrow's published bands are nitrate 10-50 mg/L, phosphate 0.1-3 mg/L and iron 0.01-0.5 mg/L - and since a shortage shows only as growth that stops, you have to measure rather than look. Handle it by the bare stem, never the leaves. Cut the top when it reaches the surface and replant the cutting, and thin the group so the lower stems are not shaded by their neighbours. Water chemistry barely matters: pH 5-9, KH 2-30, 15-30 C, and it is one of the few stem plants happy in an unheated room tank.

Diet

Feeds from both roots and the water column, but takes most of what it needs from the water, so a plain inert substrate is fine as long as the column is dosed. Because a deficiency never shows as spots, holes or yellowing - only as growth that stops - dose to a schedule and judge the result by new stem length rather than by leaf appearance.

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Frequently asked questions

What water parameters does a Water Hyssop need?

Water Hyssop does best at 15–30 °C (59–86 °F), pH 5–9 and a general hardness of 0–30 °dGH.

Where should Water Hyssop be placed in the aquarium?

Water Hyssop works best at the back of the tank and reaches around 50 cm.

Is the Water Hyssop suitable for beginners?

Yes — Water Hyssop is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.

Sources

• Bacopa monnieri – Kleines Fettblatt – Flowgrow Wasserpflanzen-Datenbank
• Bacopa monnieri 'Compact' – Flowgrow Wasserpflanzen-Datenbank
• Bacopa australis – Südliches Fettblatt – Flowgrow Wasserpflanzen-Datenbank
• Bacopa crenata – Gekerbtes Fettblatt – Flowgrow Wasserpflanzen-Datenbank
• Bacopa monnieri 'Compact' – Tropica Aquarium Plants (code 044A)
• Bacopa monnieri | Aquasabi – Aquascaping Shop
• Bacopa monnieri 'Compact' | Aquasabi – Aquascaping Shop
• AQUARIUM GUIDE – Wasserpflanzen – Bacopa monnieri – Kleines Fettblatt
• Bacopa monnieri (Brahmi, Herb of Grace, Monnier's Water-hyssop, Smooth Water Hyssop, Water Hyssop) | NC State Extension Gardener Plant Toolbox
• Centella asiatica (Asiatic pennywort, Gotu kola, Indian Pennywort, Kodavan, Marsh Pennywort, Spadeleaf) | NC State Extension Gardener Plant Toolbox
• Plant Profile: Bacopa Monnieri – Buce Plant