How to Get Rid of White Residue on Aquarium Glass and Prevent It

Goldfish tank

Certain species prefer hard water, but it's not so good for our tanks' clean, transparent glass. If you've ever observed a white residue building on the top of your glass tank, it's most likely due to evaporation. Limescale (calcium carbonate with extra ions) build-up on the glass is most likely the residue left behind.

When mineral-rich aquarium water (hard water) evaporates, the heavier components stick to one another and to the glass, leaving an unsightly, streaky white residue behind. If you have hard water, the build-up around your shower head will most likely be the same. While these residues won't harm your fish or your aquarium, they can make them difficult to notice, and spotted and streaked aquarium glass isn't attractive to look at.

Safe Removal of Lime Buildup From Glass

Lime buildup is so unsightly that it's easy to be tempted to eliminate it using household cleaners. However, resist the desire since even the tiniest drop or residue from any cleaning product would most certainly kill your fish. This restriction also applies to the tank's upper edges.

There are products available to safely remove lime buildup from aquarium glass. Look for fish-safe cleaning sprays at your local pet store. Try basic white vinegar on a dry aquarium for a more environmentally friendly and cost-effective solution. Vinegar is a natural disinfectant that also dissolves resistant lime deposits due to its acidity.

You'll need to move your fish to a holding tank for this method of cleaning. Drain the tank fully of water and remove any plants or decorations once all of your fish have been securely removed. Gravel and other substrates can be removed or left in place if a barrier keeps them from leaking. Place the tank on a cloth and pour enough vinegar to cover the damaged glass. Allow 10 to 20 minutes before scrubbing with a non-abrasive pad or towel.

If a tough spot of build-up persists, carefully scrape the scale away from only the glass panels using a razor blade or algae scraper. Any sharp instruments may readily damage plexiglass or other forms of acrylic tanks, therefore don't use a razor on them. After you've finished, properly rinse the tank before refilling it.

Preventing Lime Buildup

Preventing scale from forming in the first place is the simplest approach to avoid wasting time washing your tank. Check your tank's water line every two or three days because evaporation is the major cause of this residue. Low humidity days in the winter months, as well as warmer tank water temps, both increase the rate of evaporation.

Your remaining tank water will get somewhat harder as the water begins to evaporate (a higher density of minerals per liter of water). As a result, distilled water is the greatest substitute for evaporated hard water. Because the water that fled was pure, the water you pour back in should also be pure. All minerals have been removed from distilled water. Replacing evaporated water with mineral-rich water might lead to dangerously high levels of some minerals over time. This risk is eliminated by replacing evaporation with distilled water.

When making a partial water change in your aquarium, however, you should replenish it with your usual hard water source AFTER removing some of the old water. This will keep the minerals in check and assist buffer the pH, preventing the water from becoming acidic (reducing its pH). To ensure that your water quality is healthy for your fish, you should have a water test kit that tests pH, hardness (GH), and alkalinity (kH).