What is Algae?
Algae are a very diverse group of simple mostly unicellular organisms. Many of the various groups of algae types are not even closely related so it’s easier to understand why they can take such a wide array of growth forms, patterns and reproductive strategies among other differences. They are not plants, as even multicellular species lack the organization and specialization typical of plant cells. Algae typically function in much the same way, however- by gathering simple nutrients from their surrounds and converting them to food through photosynthesis, releasing oxygen as a byproduct. Overall algae’s needs are pretty simple and controlling these is key to controlling it.
First or all an important fact: all tanks have algae, even healthy ones. It’s a natural part of the environment you’re trying to recreate and trying to eliminate it completely is a war you are not going to win. The goal instead it to try our best to regulate its growth and to hopefully encourage less invasive species that won’t take over the tank. Allowing algae to grow for example on the back glass will go a long way towards keeping it off everything else.
What Does Algae Need to Grow?
Algae are pretty simple lifeforms with some pretty basic needs. The three main things it needs to thrive are water, light, and a food source. Obviously, being an aquarium, controlling the algae’s access to water is off the table. The other two, however, can be regulated using various techniques to prevent or eliminate problem algae.
Most algae problems aquarists experience are the result of excess light, both from the tank’s lighting itself and from natural sunlight, even indirect sunlight, being allowed to reach the tank. Even small changes in the amount of light your tank receives can have a big impact on the algae growth. Things like placing your tank away from windows or keeping the curtains closed during the day can be enough to curtail algae’s spread. Adding a timer to the tank’s lighting is also useful both for controlling the amount of light the tank receives as well as giving its inhabitants a regular schedule. Setting the lighting to only run around six hours a day will give fish and any plants a sufficient photo period while still limiting the algae’s light intake.
Keeping the algae’s food supply in check can be a bit trickier. Unlike with light you can’t tell at a glance just how much is available to the algae. Furthermore, even a healthy tank will have at least some of the two main culprits- nitrate and phosphate- present. They enter the tank as fish food. Whether it passes through a fish first or not (it should go without saying, but overfeeding if a big source of excess nutrients), it eventually ends up breaking down into these two substances. To make things worse some tap water can have a modest amount of phosphate meaning doing a water change may not be enough. Even so water changes are your best bet here at least to reduce nitrate levels, including a thorough vacuuming of the substrate. And if you find your water to contain high levels of phosphate you have a couple options- either finding another water source (such as bottled or filter) or using a special phosphate absorbing filter media. Finally, live plants can be added to give the algae some competition.
Algae Eating Animals
Adding something to simply eat the algae is an often made choice of beginning aquarists. This ends in disappointment nearly as often. You see, most species of fish, snails, and crabs that are commonly sold with the promise that they’ll make all your algae problems go away come with a few hitches. For one, many of these critters are actually pretty picky. They like only a few select varieties of algae and even if you happen to have a species they like will happily fill up on whatever you feed the rest of your fish while ignoring any algae. Many snails have the opposite problem- consuming algae veraciously and multiplying all the while. Before long the tank is nothing but snails. And even worse once the algae runs out a crash in their population often happens leading to polluted water which just leads to more algae. Finally, many of the species available to algae control just aren’t good tankmates. They either get very large or aggressive, will eat anything (like your other fish or plants), or come with some other hitch.
But, don’t let this discourage you from including some algae loving species in your aquarium setup. Instead, take it as a reminder to thoroughly research anything you add to your tank. There are many species of fish, snail, and crab that are great for controlling specific types of algae under the right circumstances.
Again, all tanks have algae. Removal is not an option. Learning to control it and achieve a happy balance is the goal. Modest algae growth is normal and in the end will provide a more natural and stable environment for your tank’s inhabitants.