Aquarium Glass Cleaning: Coralline, Calcium and Scratches

Clear glass is the first thing anyone notices about an aquarium, and the first thing they notice when it is missing. Green film is easy. The harder problems are coralline algae crusts in reef tanks, white calcium spots above the waterline and the hard water marks that build up on the outside. Aquarium glass cleaning done wrong leaves scratches that are there for the life of the tank.

This guide covers the tools and techniques our technicians use on tanks across Wheeling and the north suburbs.

Know Your Material First

Before any tool touches the tank, confirm whether it is glass or acrylic.

• Glass is hard and resists scratching, which allows metal razor blades on the inside panels when used carefully.

• Acrylic scratches easily. Razor blades and many standard algae pads will damage it. Acrylic needs plastic blades and acrylic-safe pads.

If you are not sure, assume acrylic until confirmed. Our post on glass vs. acrylic aquariums covers the differences.

Green Film and Soft Algae

Soft green film comes off with a magnetic cleaner or an algae pad. A few habits help:

• Clean before the water change so loose algae gets siphoned out.

• Keep sand away from the cleaning pad. A single grain trapped under a pad scratches glass and acrylic alike.

• Rinse magnetic cleaners often.

Coralline Algae

Coralline algae is a good sign in a reef tank, but on the viewing glass it forms hard pink and purple spots that pads cannot lift.

• On glass, a sharp aquarium-safe razor blade or scraper held at a shallow angle removes coralline cleanly.

• On acrylic, use a plastic blade designed for acrylic and work slowly.

• Stay a little away from silicone seams. Blades can cut into the seam edge.

• Regular removal is easier than letting coralline build into thick crusts.

Calcium and Salt Creep Above the Waterline

Saltwater tanks leave white mineral deposits where water splashes and evaporates. Hard water does the same on freshwater tanks.

• Inside the tank above the waterline, deposits can be softened and scraped carefully.

• Outside the tank, a cloth dampened with fresh water or a diluted vinegar solution dissolves most mineral marks. Never spray cleaners toward the tank where overspray can reach the water.

• Never use household glass cleaners with ammonia near an aquarium.

Wheeling, Buffalo Grove, Arlington Heights and Palatine all receive treated Lake Michigan water through the Northwest Water Commission, according to the City of Evanston. Using RO/DI water for top-off on saltwater tanks reduces the minerals that cause spotting. See our guide to RODI water and salt mixing.

Cleaning the Outside of the Tank

The outside is where fingerprints, dust and splash marks collect. Use a soft lint-free cloth and plain water or an aquarium-safe cleaner sprayed onto the cloth, not the tank. Dry with a second cloth to avoid streaks.

Dealing With Scratches

Light scratches on acrylic can often be polished out with an acrylic scratch removal kit, though polishing the inside requires draining the tank below the scratch. Scratches in glass are much harder to remove. Prevention matters more than repair:

• Keep sand away from pads and magnets.

• Use the right blade for the material.

• Replace worn pads before they become abrasive.

How Often Glass Should Be Cleaned

Most home tanks look their best with glass cleaned at every maintenance visit plus a quick wipe between visits. Business tanks, where appearance matters every day, usually get glass cleaned every visit without exception. If glass turns green within a day or two, the real issue is nutrients or lighting, not cleaning frequency. Our post on how to stop algae overgrowth explains how to fix the cause.

Key Takeaways

• Confirm glass or acrylic before choosing a tool.

• Sand under a pad is the most common cause of scratches.

• Coralline needs a blade, not a pad, and regular removal.

• Mineral spots outside the tank respond to fresh water or diluted vinegar on a cloth.

Frequently Asked Questions

Can I use Windex on my aquarium?

Avoid ammonia-based household glass cleaners near aquariums. Use plain water or an aquarium-safe product applied to the cloth.

How do I get coralline algae off aquarium glass?

On glass, use an aquarium-safe razor scraper at a shallow angle. On acrylic, use a plastic blade designed for acrylic.

Can scratches be removed from an aquarium?

Acrylic scratches can often be polished out. Glass scratches are difficult to remove, so prevention is key.

Work with Marine Concepts

Glass cleaning is part of every Marine Concepts maintenance visit for homes and businesses in Wheeling, Northbrook, Glenview and nearby suburbs. Request a free quote or call 847-344-2422.