Aquarium Plants & Algae: Care Guides and Algae Control

Algae questions are some of the most common in the hobby — and some of the most over-treated, since most algae is a sign of light or nutrient balance rather than a standalone problem. This section covers identifying what you're actually looking at, what's normal versus what needs adjusting, and live plant care for the species that help keep that balance in check.

What This Section Covers

Aquarium plants and algae are two sides of the same coin — both are responding to the same light and nutrient conditions in your tank, which is why plant health and algae control are covered together here. Whether you're trying to identify a growth you've found, figure out why a plant isn't thriving, or just understand what's "normal" versus what needs adjusting, this section focuses on practical identification and fixes rather than generic advice.

This section is actively expanding to cover live plant care, common plant health issues, and substrate/setup questions alongside our growing algae identification library.

Algae & Plant Guides

Algae Identification & Control

Green algae growth on the glass and decor of a planted freshwater aquarium
Aquarium Plants & Algae

Algae in Aquariums: Types, Causes, and How to Get It Under Control

Nearly every aquarium develops algae at some point — the difference between a tank with a passing algae phase and one with a chronic problem usually comes down to light and nutrients, not luck.
A thin brown algae film developing on the glass of a newly set up aquarium
Aquarium Plants & Algae

How Long Does It Take for Algae to Grow in an Aquarium?

New tank owners often expect algae to be a distant problem — but depending on the type, algae can show up within days, and a sudden bloom in an older tank usually has a recent cause.
Dark tufted cyanobacteria growth on aquarium hardscape, often confused with black beard algae
Aquarium Plants & Algae

Calothrix Algae: Identification and How to Get Rid of It

Calothrix forms dark, hair-like tufts that look a lot like black beard algae — but it's cyanobacteria, not true algae, and that distinction changes how you treat it.
A thin grey diatom film coating the glass and decor of a recently set up aquarium
Aquarium Plants & Algae

Grey Algae in Your Aquarium: What It Is and How to Remove It

Grey algae is usually diatoms — a soft, dusty film that's extremely common in new tanks and tends to fade on its own as the tank matures.
A lawnmower blenny grazing on turf algae across live rock in a reef tank
Aquarium Plants & Algae

Lawnmower Blenny and Hair Algae: What It Eats, and What It Won't

A lawnmower blenny will genuinely graze hair and turf algae — but it needs an established tank with enough algae to sustain it, and it won't fix whatever's causing the algae to grow in the first place.
A small algae-eating fish grazing on algae-covered aquarium glass next to a larger adult of the same species
Aquarium Plants & Algae

How Fast Do Algae Eaters Grow? Why It Matters for Stocking

An algae eater's growth rate determines two things: how soon it outgrows its tank, and how soon it outgrows the algae supply that justified buying it.

Live Plant Care: Anubias & Hornwort

An anubias plant with its rhizome mounted on driftwood above the substrate
Aquarium Plants & Algae

Anubias Rot: Why It Happens and How to Stop It

Anubias is one of the toughest aquarium plants, but rhizome rot — usually caused by burying the rhizome in substrate — is the main way it fails, and it's preventable.
Anubias growing emersed on hardscape above the waterline in a paludarium
Aquarium Plants & Algae

Can Anubias Grow Out of Water? Emersed Growth Explained

Anubias grows just as well — sometimes better — out of water, which is why it's a staple in paludariums and vivariums. The main adjustments are humidity and leaf expectations.
A sprig of hornwort with green new growth at the tips and browning needles lower down
Aquarium Plants & Algae

Hornwort Turning Brown: Causes and How to Fix It

New hornwort dropping brown needles right after purchase is one of the most common 'is my plant dying' moments in the hobby — and usually isn't.
Scissors trimming a healthy green sprig of hornwort in a planted aquarium
Aquarium Plants & Algae

How to Trim Hornwort (And Why It's Worth Doing Regularly)

Hornwort's biggest 'problem' is usually that it grows too well — regular trimming keeps it from shading out the rest of the tank and gives you free new plants in the process.
An Amazon sword plant sending out a horizontal runner with a small plantlet forming at the end
Aquarium Plants & Algae

Amazon Sword Runners: What They Are and How to Use Them

A long stem trailing away from your Amazon sword with a tiny new plant on the end isn't a problem — it's the plant propagating itself, and a free new plant if you know what to do with it.
Layered aquarium substrate with a dark nutrient-rich base layer capped by fine gravel, with plants rooted into it
Aquarium Plants & Algae

Aquarium Plant Substrate: Do You Actually Need a Special One?

Whether you need a dedicated plant substrate depends mostly on which plants you're growing — root-feeders benefit a lot, epiphytes barely care.

Reef Tank Plants, Algae & Coralline ID

Coralline algae, macroalgae, and turf algae growing across live rock on a coral reef
Aquarium Plants & Algae

17 Types of Plants and Algae Found in Coral Reefs (And What They Mean for a Reef Tank)

Most of what people call 'coral reef plants' are actually algae — and understanding the difference matters once you're trying to figure out what's growing in your own reef tank.
Orange coralline algae crusting over live rock in a reef aquarium alongside purple patches
Aquarium Plants & Algae

Orange Coralline Algae: A Normal Color, Not a Different Problem

Orange coralline algae looks different from the purple patches most reef keepers expect — but it's the same group of calcified algae, and its appearance is a normal color variation, not a separate issue.
A lawnmower blenny grazing on turf algae across live rock in a reef tank
Aquarium Plants & Algae

Lawnmower Blenny and Hair Algae: What It Eats, and What It Won't

A lawnmower blenny will genuinely graze hair and turf algae — but it needs an established tank with enough algae to sustain it, and it won't fix whatever's causing the algae to grow in the first place.
Reef tank alkalinity test kit with titration syringe and color-change reagent next to a glass of aquarium water
Saltwater Fish

How to Raise Alkalinity in a Reef Tank Safely

Alkalinity should sit between 8-12 dKH and should never move more than about 1-2 dKH in a day — here's how to raise it correctly with baking soda, two-part dosing, or kalkwasser.
Brown diatom film coating the sand bed and lower rockwork of a newly set up reef tank
Saltwater Fish

Diatoms in a Reef Tank: Why the Brown Dust Shows Up and How to Handle It

A brown, dusty film coating the sand and glass is one of the most predictable phases of a new reef tank's first few weeks — here's why it happens, how long it lasts, and what actually helps.

Planted Tank Setup & New Tank Basics

A well-planted 75-gallon aquarium with a mix of sword plants, hornwort, and anubias mounted on driftwood
Aquarium Plants & Algae

Setting Up a 75-Gallon Planted Aquarium: What to Plan For

A 75-gallon tank's extra height and depth compared to a 55-gallon make it a good fit for a layered planted setup — if substrate, light, and plant selection are planned together.
Layered aquarium substrate with a dark nutrient-rich base layer capped by fine gravel, with plants rooted into it
Aquarium Plants & Algae

Aquarium Plant Substrate: Do You Actually Need a Special One?

Whether you need a dedicated plant substrate depends mostly on which plants you're growing — root-feeders benefit a lot, epiphytes barely care.
Java fern leaves in a planted aquarium with small green spots of algae on the older leaves
Aquarium Plants & Algae

Algae on Java Fern: Why It Happens and What Actually Helps

Algae on java fern is usually less about the fern doing anything wrong and more about it being slow-growing in a tank where light or nutrients outpace its needs.
Fast-growing hornwort and floating plants in a planted aquarium during the early weeks of setup
Aquarium Plants & Algae

Best Plants for Nitrite Control: What Plants Can (and Can't) Do

If nitrite is spiking, the actual fix is the nitrogen cycle establishing itself — plants help indirectly by competing for the ammonia that would otherwise become nitrite.
A small algae-eating fish grazing on algae-covered aquarium glass next to a larger adult of the same species
Aquarium Plants & Algae

How Fast Do Algae Eaters Grow? Why It Matters for Stocking

An algae eater's growth rate determines two things: how soon it outgrows its tank, and how soon it outgrows the algae supply that justified buying it.

Substrate, Soil & Tank Weight

A layered aquarium substrate with a dark soil base capped by a layer of sand, with plants rooted into it
Aquarium Plants & Algae

Potting Soil in Aquariums: The 'Dirted Tank' Method Explained

Capping plain organic potting soil with sand or gravel creates a nutrient-rich substrate that can support heavily planted, low-tech tanks — with a messier setup process than inert substrates.
A 20-gallon aquarium with a layer of light-colored sand substrate being added before planting
Aquarium Plants & Algae

How Much Sand Do You Need for a 20-Gallon Tank?

A 20-gallon long and a 20-gallon high hold the same volume but have very different footprints — and footprint, not gallons, is what determines how much sand you actually need.
Reddish-brown laterite clay granules being layered into aquarium substrate beneath a layer of gravel
Aquarium Plants & Algae

Aquarium Laterite: What It Is and How to Use It in a Planted Tank

Laterite supplies iron and trace minerals to root-feeding plants from beneath the substrate surface — a traditional approach that still works well alongside, or instead of, modern aqua soils.
A bag of play sand being poured into an aquarium as substrate, with rinsing equipment nearby
Aquarium Plants & Algae

Is Crayola Play Sand Safe for an Aquarium?

Plain, uncolored play sand is a well-established budget aquarium substrate after rinsing — but 'play sand' covers a range of products, and dyed or coated versions deserve a closer look.
A large 75-gallon aquarium filled with water, substrate, and decor sitting on a sturdy stand
Equipment & Troubleshooting

How Much Does a 75-Gallon Fish Tank Weigh When Filled?

A filled 75-gallon tank weighs considerably more than the 75 gallons of water alone once the tank itself, substrate, and decor are factored in — often somewhere around 850-1000+ lbs total.
Dark green grass-like mondo grass foliage growing as a groundcover, with a separate underwater grass-carpet aquarium in the background
Aquarium Plants & Algae

Is Mondo Grass an Aquatic Plant? What Happens If You Submerge It

Mondo grass looks like it belongs in an underwater grass carpet, and it's sometimes sold that way — but it's a terrestrial/marginal plant that rots over time when kept fully submerged.

Frequently Asked Questions

Is algae always a sign something's wrong with my tank?

No. A small amount of algae is normal in almost every established aquarium, and is often a sign of a tank that's matured and developed a stable biological community. Algae becomes worth addressing when it's growing faster than routine maintenance can keep up with, or when it's smothering plants or covering decor heavily — at that point it's usually a sign of a light or nutrient imbalance worth adjusting, covered in our algae guide.

Why does my new tank have algae already?

New tanks are prone to algae — especially brown diatom film — because every surface is newly available for colonization and the tank's biological filtration hasn't matured yet to compete for the same nutrients. This is one of the most common new-tank experiences and typically resolves on its own over the first few weeks, covered in more detail in our algae growth timeline guide.