Blue-green algae thrive in general poor water conditions. They develop on your fish, which will eventually start to look moldy—especially when they’re motionless. Red algae are caused by a lack of carbon dioxide and hang all over your aquarium in threads. Brown algae thrive in conditions with a lack of adequate light and form in large, brown layers. Green algae are caused by too much light and can make your aquarium look like pea soup.

Purchase carbon dioxide boosters from pet stores and online suppliers.

Take note of leftover foods—if you see any, decrease the size of the next batch of food. Use an automatic feeder to ensure timely feeding and prevent overfeeding.

Decrease your aquarium’s light exposure to 6 to 10 hours a day if it doesn’t have plants. Connect your lights to automatic timers to control light exposure. If decreasing light exposure isn’t working, trying decreasing the intensity of your lights. Change your light bulbs at least once a year.

Nerite snails, Mystery Snails, Ivory Snails, and Gold Inca Snails are all great choices. In terms of fish for saltwater tanks, angelfish, blennies or tangs are great choices. Don’t rely solely on algae-eating species to control your problem.

Add poly filters or a carbon-phosphate remover to the tank to decrease phosphate levels.

Change water weekly to keep nitrate levels low.

If you’re adding cold water, make sure the temperature is acceptable for the species of fish in your tank. Use a water conditioner when swapping water. A 10 percent daily swap means you should be switching your water completely every 10 weeks. Do not swap more than 20 percent of the aquarium water daily. For saltwater tanks, add ½ cup (118 grams) of sea salt per 1 gallon (3. 8 L) of water and mix it thoroughly.

Never replenish your tank with well or tap water. Purchase a water filter from a home hardware store or online supplier.

Wipe off any decorations with your algae pad. For algae that is difficult to remove, use a razor blade or plastic blade to scrape it off. Never let bleach, soap, or other cleaning chemicals get into your water, as they can kill your aquatic life and beneficial bacteria. Create your own gentle aquarium siphon and vacuum if you’d like.

Don’t use algaecides unless you haven’t had any success with any other options. Most of them contain chemicals that can harm your fish.