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Nuisance Algae in the Reef Aquarium – Part II

Nuisance Algae in the Reef Aquarium – Part II
By: Scott Zachow

In Part I of this series I began by talking about some of the fuels that feed nuisance algae and described the nuisance algae that is present in our 75-gallon reef tank. The problems started in early spring of 2005 with the development of the unidentified brown wafer-like algae. The algae weren’t undesirable; in fact the growth form was quite nice to contrast the purple coralline algae that was growing abundantly in the aquarium. The mistake that I made was assuming that despite the algae growth, all of the tanks water parameters were fine and a biological balance was still in place. All algae require nutrients to grow and if there is an undesirable algae growing in your tank, it is because excessive nutrients are available for absorption. If I would have remembered this myself we wouldn’t be talking about this today, so maybe it’s a good thing that my memory slipped me in order to provide me the opportunity to help ensure yours doesn’t.

The first place for us to start was to look for Nitrates (NO3) in the tank. A test was performed on 9-17-2005 for NO3 in the aquarium and the results using a Salifert Test kit following the low range procedure resulted in 0ppm. This isn’t surprising though as the nuisance algae is most likely taking all of the nutrients in for growth. A common misconception is that a test result of 0ppm total Nitrate means that there are no nitrates present and the algae are growing for other reasons. With abundant algae to consume the nutrient as fast as it is available, the test results appear fine although the Nitrate is undoubtedly available. Determining whether it is building in the aquarium and not being exported or if it is being added unknowingly to the aquarium must be determined.

An image of the aquarium taken on 9-17-2005. Note the overgrowth of nuisance algae throughout the aquarium.

We began analyzing our problem with the source water. We started here to ensure the source water (water used for water changes and top-off) wasn’t the cause of our problem. To start, a Nitrate test was performed on the top off water. All water for our aquarium is run from our tap through an AquaFX 4-stage RO/DI unit. The 4-stage unit contains a .5 Micron Sediment Cartridge, Chlorine Guzzler Carbon Cartridge, Color Changing DI Cartridge and a 75-gallon per day RO Membrane. After producing a fresh 5 gallons of water, the NO3 tested 0ppm using the same testing procedures as above. Total Dissolved Solids (TDS) was also tested in the freshwater ran through the RO/DI unit. TDS is a measure of anything in water, whether it is calcium, magnesium or any other solid present. If you were to fill a cup of water and let it evaporate, any solid left after complete evaporation is what we are measuring for. Using a hand-held TDS meter, or other, you can perform the same test with freshly made water to determine the amount of solids present. Obviously the lower the TDS reading the better off you are since we want to add only pure water to our tanks. To continue to test the fresh top-off water, a TDS test was performed on both our tap water and the filtered water. I was surprised at the TDS of our tap water, measuring 247ppm. The filtered water wasn’t too bad with a TDS of 10ppm. I wouldn’t suspect that a TDS of 10ppm would be a problem in the tank and therefore will not act on the make-up water at this time. If no other sources are found we may have to move back and re-evaluate this decision.

Another image of the aquarium showing the various overgrowth of algae.

Since we can assume at this point that the source of the nutrients feeding the algae in our tank isn’t coming from the source water, there has to be some other source of nutrients. However top off water is not the only addition made to the tank. We continue to look at the possibility of NO3 being added into the aquarium so we shift our focus other miscellaneous additions. We do not use any additives with our tank. The only thing that is added to our aquarium other than source water is food. We use a variety of flakes from Ocean Nutrition but add them sparingly. The main source of food is from 1 cube of Hikari Frozen Brine Shrimp and one cube of Hikari Frozen Mysis Shrimp. The food was considered a possibility due to previous studies that have been performed on their actual ingredients (Shimek, 2002) and also because it is noted that the liquid from frozen foods can be a significant source of nutrients, as well as uneaten food in general. Up to this point we were very mindful about how much food was added to the aquarium with only small pinches of flake and the 2 cubes per day provided. To feed the cubes we allowed them to thaw in a cup of water and once thawed, dumped the contents of the cup into the tank. Since mid August, 2005 we changed our procedure to eliminate the thawed, nutrient rich water from being added. Our new method of feeding the frozen food is to allow it to thaw and then strain the food through a fine net (fish net works great). Once the thawed shrimp is in the net we place it into the tank and turn it inside out in front of a current source, which blows the food throughout the aquarium. This was an easy fix and although the outcome of this change cannot be measured, we do know that we have reduced the amount of nutrients being added to the tank.

Taken on 10-6-05 this image shows the progress that is being made in the reduction of the nuisance algae through various techniques.

As mentioned above we do not add any supplements into the aquarium. For Calcium and Alkalinity we use a My Reef Creations Dual Chamber Calcium Reactor filled with Knop Korallith 1.8-2.5mm media. Although others have mentioned that the reactor is probably not any part of the problem, I am unsure. What leads me to this uncertainty is that the pH is our tank is significantly lowered when running the reactor (as suspected). The low pH is obviously from the CO2 and probably from the NO3 as well (since increased NO3 will depress pH). The second thing that concerns me about the reactor is that the effluent line has a nice coating of green algae inside which is not present in the hoses from the pump to the 1st chamber, or in the hose from the 1st chamber to the 2nd chamber. The feed hose for the reactor, which is connected to a Maxi-Jet 1200 does not have this discoloration either. To see if there was any Nitrate present in the reactor, a cup was filled with the reactor effluent and tested using the same procedures for testing the tank water and freshwater used for top-off. As with the rest of the test, this water test also resulted 0ppm. Something was different with this though. I noticed when the cup was filled with the reactor effluent that the water had a foul smell. I also noticed this when opening the Salifert vial to complete the test by comparing the water to the chart by looking through the top. Perhaps the water is stagnant in the reactor? Perhaps the stagnant water contains nutrients other than NO3 that is fueling the algae? In order to try to flush this water out, I took 2 steps. On 9-17-2005 the CO2 feeding the calcium reactor was shut off. This was done to see if the pH would rise and have any change in the growth of the algae. I also opened up the effluent from the reactor slowly. I did this slowly in order to not drop the pH significantly by flushing out low pH water from the reactor. The hope here was that flushing out the reactor (and eliminating the foul smell) would if nothing else help ease my mind. The reactor was basically shut off for 8 days and during this time there was no change in the pH, which tells me that the pH is suppressed due to the excessive Nitrate that is somewhere. On 9-25-2005 the reactor was placed online only after noting the foul smell originally encountered from the effluent was gone. I also hoped that placing the reactor back online would increase the Alkalinity and offset any negative effects that the low pH might cause; particularly coral growth since it reduces corals ability to calcify.

With all of the external sources looked at, it was time to look at the internal causes and see what could be done to address them. This tank employs a Bare Bottom, which is one without any substrate. The purpose of changing to a bare-bottom tank was to allow us to increase the amount of flow in the tank for the SPS corals that we keep. This also adds problems since without any form of substrate there has to be a mechanical source to remove excessive waste before it is converted to NO3. This can either be by keeping the detritus in suspension for removal or through manual siphoning. Since we have had out aquarium setup in this manner, bi-weekly 5-gallon water changes were performed during which time we siphoned the detritus. Even though we have over 3,700gph flowing through the tank it is not enough to keep all the detritus in suspension. During the two weeks between the water changes piles still accumulated and had to be removed. To counter this, we increased the frequency and amount of water changed. Since we do not use any natural forms of nutrient export (refugium with macroalgae that is manually removed for example) it was determined that the frequency of our only main export mechanism needed to be increased. We are now performing between 10-15 gallons of water every week, 5-gallons 2-3 times per weekend. This is an increase from 13% per month to nearly 67% per month of our water being changed. During each of these changes the accumulated detritus is also removed from the aquarium.

Another image showing the reduction in nuisance algae.

In addition to water changes, our secondary source of nutrient export is through Protein Skimming. We utilize a My Reef Creations MR-1 skimmer powered by a MAG 18 pump. As with our water changes, we also increased skimmer production and the frequency of maintenance. In order to keep a skimmer efficiently skimming, the skimmer should be cleaned often. This was typically done bi-weekly and is now also being performed weekly with our water changes. The type of product from the skimmer has also changed from a cup full of dark dry product every week to a lighter colored and wetter product every few days. In order to keep the skimmate production we are looking for the skimmer is adjusted daily or every two days to ensure optimal production. The goal is to reduce the amount of Dissolved Organic Compounds (DOC’s) before they have a chance to contribute to Nitrate. Since water changes and protein skimming is our only methods of nutrient export, at the moment, we felt like we needed to maximize the export capacity of these two forms to reduce the available nutrients and to starve out the algae.

Another image showing that through persistance nuisance algae can be controlled.

Through all of this, I am pleased to report that we are already seeing a reduction in the nuisance algae in the aquarium and are seeing an overall improvement in the health of our animals. There is still a significant amount of progress that needs to be made. An abundance of the various nuisance algae remains in the aquarium. Through all of our efforts to date the most significant decrease as been in the Valonia sp. algae. This is reverse from what I thought since I was expecting this to require aggressive manual removal. Secondly are the Derbresia and lastly the Bryopsis, which seems to be the only one that is still steadily growing. I am confident that we are on the right path though as has been proven through the reduction. Addressing the accumulation of nutrients that build up in the tank appears to be the way for us to beat this problem. However it was important for us (and you) to go through the steps to find the real cause of the problem and correct it. Next month we will provide you with an update of our progress. Until then…

Reef On!
Scott Zachow