ReefDen

Care guides

No-fluff guides, written by reef-keepers.

Cycling, chemistry, lighting, aquascaping, fish health — the articles we wished existed when we started.

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All guides

Beginner

How to cycle a saltwater tank (the right way)

Cycling builds the bacterial colonies that keep fish alive. Done wrong it kills livestock. Here is the patient, no-shortcut version.

Apr 15, 2026Read
Beginner

Your first saltwater fish: 7 species that won't break your heart

Once your tank is cycled, you need a hardy fish that survives beginner mistakes. These seven species have a track record.

Apr 12, 2026Read
Beginner

Saltwater vs. freshwater: an honest comparison

Saltwater isn't 'just freshwater with salt added.' Here's what's actually different — cost, livestock, time, and the satisfaction at the end.

Apr 10, 2026Read
Beginner

Equipment essentials: what your first reef tank actually needs

Strip out the marketing. This is the gear list that matters for a stable, beautiful first reef — and what you can defer.

Apr 8, 2026Read
Water Chemistry

Water chemistry, demystified: salinity, alkalinity, calcium, and friends

Reef chemistry is intimidating. It shouldn't be. Here's what each parameter actually does, what numbers to target, and why.

Mar 28, 2026Read
Equipment

Reef lighting 101: PAR, spectrum, and what your corals actually need

Behind every coral that grows is a light it likes. Here's how to think about lighting without getting lost in the spec-sheet weeds.

Mar 25, 2026Read
Water Chemistry

Water changes: how often, how much, and how to make them painless

Water changes are the single most reliable maintenance task in reef-keeping. Done right, they're 30 minutes a week. Done wrong, they hurt.

Mar 20, 2026Read
Aquascaping

Aquascaping fundamentals: building rockwork that actually works

Aquascaping is part art, part flow plumbing. Here's how to build a rockwork that's beautiful, stable, and supports a healthy reef.

Mar 15, 2026Read
Fish Health

Quarantine: the unsexy practice that saves your tank

Quarantine is dull, slow, and the single most effective thing you can do to prevent catastrophic fish loss. Here's the protocol.

Mar 10, 2026Read