NilocG Thrive C vs Seachem Flourish: Complete or Supplement?

They are not the same product

This is the mix-up that stalls more planted tanks than any other. Both bottles say "for planted aquariums," but they do different jobs. A complete fertiliser has both macros (nitrogen, phosphorus, potassium) and micros (iron and trace elements). A supplement has only part of that. Buy the wrong one to use alone and your plants slowly starve for whatever it leaves out.

What each one is

• NilocG Thrive C — complete. An all-in-one with N, P, K and micros, tuned low for low-tech tanks. One weekly dose covers everything a water-column plant needs.
• Seachem Flourish — supplement. A rich trace/micro blend, but Seachem's own page states it "does not contain significant levels of nitrogen or phosphorus." It is designed to supplement micros, not to feed a tank on its own.

Run Flourish alone and plants starve

Dose only Flourish and your plants get iron and trace elements but no nitrogen or phosphorus to build tissue — so growth stalls and older leaves yellow and die back. That is not a knock on Flourish; it is doing exactly what it is designed for. It just is not a standalone fertiliser, and a lot of beginners buy it thinking it is.

When Flourish is the right call

Flourish shines as a top-up next to a macro source: if you dose dry salts or a macro-focused fert and just want to add trace elements, Flourish is excellent. It is also a fine iron/micro booster for a tank that is otherwise fed. (The same logic rules out API Leaf Zone as a standalone — it is essentially iron and potassium, no N or P — good as a cheap top-up, not a complete fert. See our full guide to fertilising a low-tech tank.)

Bottom line

Want one bottle that does it all? Buy NilocG Thrive C — it is complete. Reach for Seachem Flourish only to top up trace elements alongside a macro source, not as your only fertiliser. Read the label: if it does not list N, P and K, it is a supplement, not a standalone.