Algae Effects on Fish

Sorry to tell you that if you add fish to water, you will get algae. No matter how diligent your quarantine, you can’t avoid it. So what can you do to minimize your algae effects on fish?

Should I be worried about algae effects on fish?

Remember: people hate algae; fish don’t really mind it. The biggest concern with a mass of algae is if you only run your filtration sporadically. During the day, algae is happy photosynthesizing and creating oxygen. However, when the sun goes down, algae will start to use the oxygen in the water. Algal respiration produces carbon dioxide, and without an adequate kH, your pH will start to drop. Lack of oxygen and suddenly swinging pH can seriously hurt your fish and kill them.

Before reaching for the anti-algae agents, check their food supply. High nitrates or phosphates will cause you to have lots of extra algae growth. High nitrates can also be bad for your fish, so make sure you’re doing your regular water changes or consider adding some plants or adding an aquaponic setup.

Cellular Algae

Also known as “pea soup” algae, these little cells can create a green pond where you can’t see the fish. Some owners swear these conditions cause their fishes’ colors to become more saturated.

Best Treatment: UV Light

Sure, a UV light won’t do a thing to treat your fishes’ bacteria or parasites, but it will kill your algae. This method is 100% safe for fish. Keep in mind that when you first kick this on, your pond will change from green to grey or brown. You will need to wait for the particles to settle out and be removed by your filtration. Adding dense floss matting to your filtration can help correct this situation faster.

Other Treatments

• Liquid algaecide – If you have used these products for years and your fish are happy with it, you can continue to do so. Not all fish react well to these products. Be sure you know your exact pond volume before treating!!

String Algae

You may see your fish nibbling on string algae and think they’re finally eating their vegetables. Sorry, but they’re actually eating all the bugs and larvae that use the algae as a home.

Best Treatment: Brush + Barley + UV Light

Yes, that’s good old manual labor! If your pond can manage a light brushing or scrubbing, your UV light will zap the rest of it. Using barley extract, bales or pellets is a great preventative measure, but it won’t remove any algae that’s already set up shop. If you use a rake, make sure it does not damage your liner or other equipment.

Other Treatments

• Granular algaecide – These granules work best when algae is out of the water, such as on a waterfall or stream that is turned off for a short period of time. It is safer for fish than the liquid treatment. Liquid algaecides don’t work well against string algae.

Saltwater Algae – Red, Brown & Green

There are MANY types of algae that like to lurk around marine aquariums. If you are growing corals, it may be a fine line between phosphate for corals and phosphate for algae. Always check your lights to make sure your algae isn’t getting some extra UV support!

Best Treatment: Scrubbing and Suction

Again, manual labor wins! Use an appropriate scrub to clean the glass on your aquarium. Using a piece of rigid airline connected to airline tubing creates a great suction device for getting into small cracks and crevices. You can vacuum your corals without damaging them this way.

Do NOT USE for Algae

• Potassium permanganate – This is the equivalent of using an atom bomb to clean your bathroom. Just do some actual cleaning and you’ll be fine. Misusing PP can obliterate your biological filtration and hurt your fish.
• Fluconazole – Don’t be lazy. Test your water and clean your tank.
• Algae “binders” or “coagulants” – Sure, these products might bind together lazy, dead algae particles, but we’ve also seen them stick gills together. Avoid using or do so very sparingly.
• “Enzyme” products – These may munch on dead algae, if the bacteria still alive, but they won’t do a thing against live algae!
• Pond dye – This may help deter algae growth and give your fish some UV protection, but not all products are fish safe! Install more permanent shading to prevent having to use unnecessary chemicals over and over.