Brown Diatom Algae Control
March 30, 2010 – 5:48 am | No Comment

What are Brown distom algae? Why do they grow in our aquarium and how to get rid of them. In this post you will find valuable information about this algae and how to control them.

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Algae Control With Flourish Excel

Submitted by on March 25, 2010 – 5:47 am2 Comments

Flourish Excel is a source of organic carbon that can be used as an alternative to Co2 injection. Though not marketed as such, Flourish Excel has proven to be very effective at controlling algae when used at dosage above the recommended levels. In this article, we will have a look at 3 different ways of using Flourish Excel for algae control: the full tank treatment, spot treatment and the Excel bath.

Flourish Excel vs Algae

Unfortunately, what makes Flourish Excel an effective algicide is unclear and Seachem is avoiding the question due to Federal regulation. According to what I found online, Flourish Excel appears to be a glutaraldehyde based compound; a disinfectant used for cold sterilization of medical and dental tools, used in tanning hides, and as a chemical preservative.
Also according to information found online, glutaraldehyde is toxic to most algae at concentrations of 0.5 – 5.0 ppm. Fortunately, these levels are not harmful to “most” aquatic plants and animals. Its effect on different forms of algae is variable, being particularly effective on the fur/hair algae and brush algae, but less (though still effective) against the staghorn algae. (Do you know any others?)


As stated previously, the use of Flourish Excel for algae control should not be harmful to “most” aquatic plant and animals. However, you have to keep in mind that glutaraldehyde is toxic so you have to be very careful and always be ready to do a water change if needed. At the dosage recommended for algae control adverse reactions have been observed in some aquatic mosses (like riccia and pellia), liveworths and vascular plants.

Full Tank Treatment

Treating the whole tank at once is certainly the easiest and most popular way to control/kill algae with Flourish Excel but it is also the most risky. Basically, all you have to do is to dose 2-3 times the recommended dose every day until the algae are gone. According to what I found on the many forums out there, most problems happen when dosing 3 times the recommended dose. I rater be safe than sorry so I never use more than 2 times the dose. Seachem recommends 1ml/10 gallon daily and 5ml/10g after a major water change. Twice the dose would be 2ml/10 gallons daily and 3 times the dose would be 3ml/10 gallons daily. At 2 to 3 time the dose, the effects I saw were not immediate but was noticeable after about my 3rd overdose in a week.

Whatever the dose you chose to use, it is always a good idea to proceed slowly. Start with the recommended dose and increase slowly. Be prepared to perform a water change if you see any problems. Remember, if you overdose too much, it can kill everything in the tank!

Spot Treatment

My favorite way to use Flourish Excel for algae control is to spot treat a small patch of algae with a syringe. Spot treating takes a bit more time, but is pretty easy to do and not as risk as a full tank treatment. To spot treat, turn your filter off to stop water flow, and inject Flourish Excel directly onto the algae you want to kill using a syringe. When I use this method, I only use the recommended dose of 1ml/10 gallons so it’s pretty safe. Some others will spot treat twice a day with 1ml/10 gallons each time. After the treatment, leave your filter off for about 30 minutes then fire it back up.

The Excel Bath

An other very safe way to use Flourish Excel for algae control is to remove the algae infected plants, rocks or driftwood and place them in a solution of 25% Flourish Excel and 75% water. After 5 minutes, rinse the plants and ornaments and place them back in the tank. This technique worked great every time I tried.

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