Things that can go wrong: Part 2

(Unedited version)
Originally appeared in the October 2005 issue of
Tropical Fish Hobbyist Magazine

Last month we started looking at some of the things that can go wrong in your planted aquarium. Generally the problems dealt with plants not growing, this month we'll look at algae growing too much. Algae are the planted aquarium keeper's constant nightmare, but with your work and perseverance they can be controlled.

The Thing About Algae

Now after saying that I would like to make it clear that the algae itself is almost never a danger for your fish. Algae can hurt your plants if they're so thick that it prevents the leaves from getting light. If you have that much algae you should clean it manually.

Algae occur naturally world wide. The real issue with algae isn't how terrible it is, but that it's not aesthetically pleasing to the aquatic gardener. Algae are quite natural and your fish will probably be just as happy with it as any higher plant. So if you have an algae problem, Don't Panic!

Trying to Keep it Out

Algae are pretty much all over. They can come in to your tank on plants, inside the fish (yes the algae can go through the fish and come out the other end and start growing again) or even in dust.

Some folks go to great lengths to try to keep the algae out of the tank in the first place. All items are sterilized; fish are quarantined until they're "cleaned out." Even the plants are dipped to kill algae, snails or anything else on them. Usually these dips kill a good portion of the plants too. It's difficult to keep a tank that sterile. I don't think I'm controlled enough to do it, nor would I personally like that sort of system. However I do believe that everyone should choose the techniques that best suit their needs and personality and if this seems like a method you'd like to try, then you should try it and see for yourself if it's something that works for you.

Don't Feed YOur Algae

I believe that algae are something you live with and keep under control. The best way to keep the algae in check is to not feed it. The old saying "Nature abhors a vacuum." is very easy to see illustrated in the aquarists battles against algae. If there are extra nutrients in your tank algae will come to use them. You want your fish, plants and good bacteria, to eat anything in the tank before the algae can get to it.

Your goal is to get your tank to a moderate state of balance and keep it there. Plant fairly heavily from the start and use several plants that should grow quickly in your mix. Watch your tank daily so if a problem does start, you'll catch it in the early stages.

There is a point where you will eventually get to if you are growing plants successfully. They will outgrow their space. They will crowd each other and they will need to be trimmed regularly. Don't wait until they're already choking each other out. Just like anything else, having a nice aquarium takes time and hands on work. No chemical or additive is as important to your aquarium as you yourself are.

Too Much of a Good Thing

Sometimes when a small problem like algae comes up, the new hobbyist may tend to panic and try to take drastic measures to fix the problem. This often causes more problems than the algae were to begin with. Remember the key to long term success is to keep a stable healthy environment. Rapid extreme changes should generally be avoided. Review the recommended cures from various sources. Decide which is most likely to logically apply to your aquarium, and then make one change at a time. Wait until there's a real chance to observe results before trying new changes.

Be careful to not upset your system and invite an algae outbreak. Don't do a bunch of new things at once. If you trim all your plants down, put on new lights, and add new fertilizers, in the same week, you're going to overload your system. Your plants won't keep up and you'll get blooms of algae and maybe even small invertebrates.

Regular maintenance and long term stability are the secret to algae free, or at least nuisance free tanks. Keep your equipment in top shape, do your water changes, and keep your plants trimmed regularly to have your tank looking its best at all times.

Encrusting Algae

These types of algae are often not considered a problem in most aquariums, and are sometimes considered as a sign of tank health. These algae are usually dark green and form hard spots. If they get on the glass they can usually be rubbed off with a sponge, credit card, or razor.


Diatoms will generally show up in a newer aquarium or one that has had a major upset. These algae usually look like a brown film over the tank glass, and surfaces, including plants. They can also feel greasy.

Diatoms are easy to remove manually with an aquarium sponge, or the side of an old credit card. Usually snails are pretty good at cleaning it up too. Diatoms will usually go away on their own as the tank becomes established or re-established. Good water changes and gravel cleaning will often help.

Green Water

Green water can start as a light cloudiness to your tank that soon becomes a thick pea soup like consistency. This is caused by lots of nutrients in the water under good lighting. It doesn't hurt anything; in fact I've noticed that my plants usually do quite well despite the green water, but it does make it hard to see the tank. Many animals utilize green water as a good food, including daphnia, a live food favorite, and fish fry.

Once again the key to getting rid of green water is usually more maintenance. Do water changes with good gravel cleaning and keep any filters you use rinsed, or changed as needed. If you're adding fertilizers stop using them while you're having the green water problem.

There is a strange little twist on green water and water changes. Sometimes the water changes actually trigger the green water. This is how it works: the green water algae are already in your tank but aren't showing up because there is some nutrient in the water they need, but have run out of. When you do the water change the missing nutrient is provided and you get a new bloom.

What should you do when this happens? Keep doing the water changes. You may consider adding more plants, particularly floating plants or even cutting your lighting somewhat. The reason you want to keep up with the water changes is to get the tank clean, and eliminate other excess nutrients in the water column, while encouraging more plant growth.

Blue-Green Algae

Blue-green algae are really not algae but cyanobacteria, photosynthesizing bacteria, and probably the first organisms to start photosynthesizing. Thank the cyanobacteria for our oxygen filled atmosphere. Despite their helpfulness to our atmosphere, they aren't really desirable in the fish tank. They're slimy, usually a bright blue-green color, and smell musty.

As with diatoms, and green water, water changes and cleaning the gravel are helpful for getting rid of cyanobacteria. There is an added way to get rid of it, and that’s using an aquarium medication for bacteria that contains erthomyacin. This usually will get rid of the cyanobacteria but it will come back if you don't get your aquarium in balance. Clean your filters if you use them, keep doing your water changes, and look for dead matter in the aquarium. I have found that some driftwood seems to be more likely to attract cyanobacteria, if you have wood and a problem with blue-green algae, you may also consider removing the wood.

Hair Algae

Hair algae are the bane of the planted aquarist and grow on almost anything. It comes in many types but they are generally in long strings of some sort, and unwelcome. The best way to get rid of it once you have it is by removing it. Fortunately you don't have to do all the work of removing hair algae yourself. There are several helpers that can work on getting the job done. Algae eating fish, snails and shrimp can all be used to help keep the aquarium clear of algae. Different animals will eat different algae. Remember your hair algae, isn't necessarily the same hair algae your neighbor has, or even the same type as the one in your tank in the other room. These common names encompass a large group of different algae. Likewise your shrimp may be good at eating some kind of hair algae but not others.

Red Algae

The red algae we usually see in the aquarium are black in color. They can look similar to the hair algae. These are usually hard to get rid of. Most animals won't eat them. Ameca splendens will eat at least some of the black brush types. Otherwise most of the red algae are a bit more controlled in their growth than the hair algae and you can sometimes learn to live with them, taking a bit out when you clean the tank, like the aquarium plants you trim.

Do Your Homework

If your goal is to have one or a few mixed community tanks with assorted plants and minimal algae growth, then your best bet is to choose a group of algae eating animals that will live together and compliment them with a few other well chosen fish. Doing your homework and knowing your plants and animals before you purchase them will ultimately give you the best results. Remember to keep your tanks clean and do regular maintenance. Your best key to success is always going to be what you put into your tank. I've seen a lot of different great set ups that can be totally different in structure and theory but what is common in all of them, is the time the aquarist puts into the project, and their perseverance to succeed despite set backs.

Questions or Comments?

If you have questions or Comments about this column, join the Natural Aquariums Forum and post them here.

Welcome to the Jungle | Into The Forest | The Creepy Crawlies | A Clearing in the Thicket | Algae Eaters for the Planted Aquarium
North American Natives | Why things go wrong Pt 1 | Why things go wrong Pt 2 (Algae) | Algae Eating Shrimp | Lo-Tech Tanks
Welcome to the Fish Room | The Stemmed Plants | Mosses | A Livebearer Biotope | Planted Tank Social | The Genus Hygrophila | Cyanobacteria
Easy Plants | What I Did Last Summer | Decorations in the Planted Tank | Botany-An Introduction to Plant Biology | Botany-Anatomy of a plant
Botany-How Plants Work | Easy Rosettes | Going High-Tech | Floating Plants | Dealing with Success | Bringing the Outside In | Vallisneria
Hair Algae | Flowering Aquarium Plants Part 1 | Flowering Aquarium Plants Part 2 | Liverworts in the Aquarium | Elements of Design
Planted Aquarium Maintenance | More Mosses | Invaders | Ferns in the Aquarium | Setting up a Planted Aquarium
Seaweeds of the Pacific Northwest | Proserpinaca | Hardware for the Planted Aquarium | Rotala | Neocaridina Shrimp | Lo-tech Tank Tips

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