Seachem Flourish 500 ml and Seachem Flourish Potassium 500ml Bundle Review (2026)

Who this bundle is for

This pack combines a bottle of Seachem Flourish, the company's base freshwater plant supplement, with Flourish Potassium, a concentrated potassium-only additive. It fits a planted tank owner who is already running a fertilizer routine and has noticed signs of potassium deficiency, such as pinholes or yellowing on older leaves, or who wants a coordinated starting point for a new low to mid tech tank. It is not aimed at someone starting from zero on nutrients, since neither bottle supplies nitrogen or phosphate on its own. Owners running a high-light, CO2-injected tank with fast-growing stem plants are the most likely to notice a real difference from the added potassium.

What is actually in each bottle

Flourish is a comprehensive supplement built around a broad base of trace and micro elements plus calcium, magnesium and iron, dosed at one capful, 5 mL, per 250 liters or about 60 US gallons, once or twice a week. Flourish Potassium is a separate, much more concentrated product derived from potassium sulfate, listed at 50,000 mg per liter of potassium, and it contains no phosphate or nitrate. The standard dose is one capful, 5 mL, per 125 liters or about 30 gallons, which raises potassium by roughly 2 mg per liter. Because the two nutrients are split into separate bottles, you dose them on their own schedules rather than mixing everything into a single weekly cap.

Fitting it into a dosing routine

Living with this bundle means keeping two bottles in rotation instead of one, which is a small extra step compared with a single all-in-one fertilizer. Many aquascapers already run Flourish alongside Flourish Nitrogen and Flourish Phosphorus from Seachem, and this bundle slots potassium into that same system without adding nitrogen or phosphate that could push a low-tech tank toward algae. Both bottles are liquid concentrates, so storage is simple, and a full 500 mL bottle of Flourish Potassium lasts a long time at the 30-gallon dosing rate. The two-step process does mean it is easier to lose track of which nutrient was dosed on which day, so a simple written schedule helps avoid over or under dosing potassium relative to the rest of the routine.

Honest trade-offs and how it compares

The clear limitation is that this bundle still leaves out nitrogen and phosphate, so a high-tech planted tank running heavy CO2 and strong light will likely need Flourish Nitrogen and Flourish Phosphorus on top of this pairing. Compared with the Flourish and Flourish Excel bundle, which pairs the same base Flourish with a liquid carbon source instead of potassium, this potassium version is the better pick specifically when leaf yellowing or stunted new growth points to a potassium gap rather than a carbon limitation. Against a single larger bottle of Flourish alone, this bundle is worth the extra cost only if potassium is genuinely the nutrient you are short on, since dosing potassium without a deficiency does not help growth.

Verdict and who should look elsewhere

Choose this bundle if you already run a base Flourish-style routine and want a straightforward way to add potassium without disturbing your nitrogen and phosphate dosing, keeping our score of 8.6 out of 10 in mind as a reflection of good value for a targeted, coordinated pair rather than a complete fertilizer system. Skip it if you are setting up nutrient dosing from scratch and need nitrogen and phosphate covered first, or if you have not seen any potassium deficiency symptoms, in which case a single bottle of Flourish or an all-in-one liquid fertilizer is a simpler starting point.

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