Frodo Stone

Also sold as Elderly Stone · Ancient Stone · European Manten Stone · Frodo

Synonyms Frodo rock

Frodo Stone is an aquascaping rock sold by the piece, typically around 14 × 10 × 9 cm (5.5 × 3.9 × 3.5 in). In the water it raises KH and GH, does not tint the water, and sinks straight away.

At a glance

Material	Rock
Raises hardness	KH and GH
Tannins	None
In the water	Sinks right away
Edges	Smooth
Prep	Rinse
Default size	14 × 10 × 9 cm (5.5 × 3.9 × 3.5 in)

Before it goes in

Frodo Stone raises KH and GH, so it pushes the water harder and the pH up over time. In a soft-water tank — Chili Rasbora and Green Neon Tetra — use a little of it or leave it out.
Before it goes in, rinse it.
5 different pieces of Frodo Stone are modelled, so the one you place looks like one you could actually pick out of the bin.
A default piece is 14 × 10 × 9 cm (5.5 × 3.9 × 3.5 in); you can stretch it to whatever you bought.

Does it raise pH and hardness?

Yes — it raises KH and GH, and pH follows. You can check any piece yourself: a drop of vinegar on it fizzes if it is the kind that dissolves.

Do I need to prepare it?

Yes: rinse it before it goes in.

Will it tint the water?

No.

What it goes with

Plants you can tie or glue straight onto it: Anubias nana 'Petite', Subwassertang, Anubias barteri and Bucephalandra 'Green Wavy'.
Substrates that pull the other way and soften what it hardens: ADA Amazonia, Akadama and UNS Controsoil.

Often compared with

	Frodo Stone	Ancient Pagoda Stone	Black Mountain Stone
Raises	KH and GH	KH and GH	KH and GH
Tannins	None	None	None
In water	Sinks	Sinks	Sinks
Prep	Rinse	Rinse	Rinse

More hardscape

Plan a tank with Frodo Stone →

Sources (3) · checked Sep 2026