Seachem Flourish Freshwater Plant Supplement 500 ml Review (2026)

Who this supplement fits

Flourish is aimed at freshwater planted tank keepers who want a broad trace element supplement rather than dosing individual nutrients separately. It works as a base layer in a fertilizing routine, commonly paired with other Seachem products for nitrogen, phosphate, or potassium when a tank needs more targeted macro nutrients. The 500 ml size suits small to medium tanks that will get through a bottle over several months of weekly dosing rather than very large tanks that would burn through it quickly. It fits both beginner and experienced keepers who want one bottle to cover most of the trace and micronutrient bases without formulating a custom fertilizer mix from raw chemicals.

What it contains and how to dose it

According to Seachem, Flourish supplies potassium, calcium, magnesium, iron, and a range of other trace elements formulated to work alongside other macro and micronutrient supplements rather than stand entirely alone. The standard dosing guidance calls for one capful, about 5 mL, per 250 liters, roughly 60 US gallons, dosed once or twice a week depending on plant density and growth rate, with each thread on the cap measuring about 1 mL for finer dosing in smaller tanks. Seachem recommends refrigerating the bottle starting about three months after opening to help preserve it, which is worth noting for anyone used to shelf-stable fertilizers that need no cold storage.

Fitting it into a fertilizing routine

Because Flourish focuses on trace and micronutrients rather than the three major macronutrients of nitrogen, phosphate, and potassium, tanks with heavier plant mass or faster growth typically need it paired with a macro supplement to avoid nutrient deficiencies showing up in new leaf growth. Dosing more than the tank's plants can use, particularly in a low-light setup where plants are not growing fast enough to absorb the extra nutrients, risks feeding algae rather than plants, so it helps to scale dosing to actual light and CO2 levels rather than a flat schedule. Weekly water changes also reset any nutrient buildup from consistent dosing.

How it compares with other trace supplements

Seachem bundles Flourish with companion products like Flourish Potassium or Flourish Excel in combo packs that score slightly higher, mainly because they cover more of a tank's nutrient needs in one purchase rather than requiring a separate order later. The larger 2 liter bottle and smaller 100 ml and 250 ml sizes let buyers match volume to tank size and dosing frequency without changing the underlying formula. Across the wider trace element category, Flourish remains one of the most established and widely stocked options, which makes sourcing replacement bottles straightforward compared with smaller niche brands that may be harder to find at a local fish store.

Verdict and who should pick something else

Flourish is a dependable, well-documented trace element supplement for anyone running a freshwater planted tank who wants a broadly trusted product rather than mixing dry fertilizers from scratch. The 500 ml size is a sensible starting bottle for small to mid-size tanks dosed weekly. Pair it with a macro nutrient supplement if plants show deficiency symptoms, since Flourish alone will not cover nitrogen or phosphate needs on its own. Keepers in low-light, low-tech tanks should dose conservatively to avoid feeding algae, and anyone wanting an all-in-one macro and micro blend may prefer a combined product instead.

Frequently asked questions