Freshwater R&D At Monterey Bay Aquarium
This article published in the January 2001 Issue of Drum & Croaker, an electronic magazine. Mark Faulkner is an Aquarist at Monterey Bay Aquarium and may be reached at mfaulkner@mbayaq.org. Pics of the aquarium appear in Mark's Sfbaaps Gallery Page.

Introduction:
In February 2000 I began a project behind the scenes at the Monterey Bay Aquarium to setup a 500-gallon R&D aquatic plant display. My goal was to recreate an Amazonian flooded forest, using plants and animals native to the Amazon River Basin. The tank was designed to promote luxuriant plant growth, using carbon dioxide injection, metal halide lighting, and nutrient supplementation. Over time, this aquarium went through some interesting changes. The first four months of setup the tank showed moderate growth by the large swords, while some plants, mainly low foreground plants, slowly withered and died. The next two months the tank was choked with filamentous algae. During the last three months, however, the display showed incredible plant growth, with zero filamentous algae growth. Over the last nine months I changed many variables in order to obtain a stable, healthy system. This article describes the plants and animals in this aquarium, approaches I took to obtain a lush display, and mistakes I made along the way.

Plants and Animals:

Plants:

• 5 Echinodorus paniculatus 6 E. cordifolius 5 E. rigidifolius 60 E. tennellus 50 E. quadrocostatus 1 E. apart 3 E. ‘Rubin’ 1 E. ‘Oriental’ 2 E. ‘Rose’ 7 Eleocharis montevidensis 5 Hydrocotyle leucocephala 100 + Sagittaria subulata
• Lemna major

Animals :

• 11 Symphysodon aequifasciata - discus 50 Hemigrammus bleheri - "rummy-nose tetra" 60 Otocinclus affinis - "otocinclus" 4 Farlowella acus - "twig catfish" 3 Crossocheilus siamensis - "Siamese algae eater"
• 130 Cardina japonica - "Yamato shrimp"

Sword plants made up the majority of the vegetative life in this display. Echinodorus tennellus, E. quadrocostatus and Sagittaria subulata were in the foreground. All of these plants produced runners and eventually filled in the foreground to make a "lawn" at the front of the tank. The back was filled in by a variety of large swords such as Echinodorus ‘Rubin’, E. cordifolius, and E. rigidifolius. The rest of the plants were used as accent plants because of leaf color and or shape. The display contained eleven wild discus measuring 4-6 in. and 50 rummy-nose tetras. Four twig catfish (Amazon natives) were placed in the tank because of their interesting morphology as well as for algal control. The rest of the animals are not native to the Amazon, but were used solely for their roles in algae control as well.

Plumbing:
The aquarium dimensions were 75"x 24"x 25". Water left the tank via a weir box mounted on the outside of the display tank, where it passed through a prefilter and continued into an 80-gallon sump located beneath the display. The sump contained all heaters, a UV sterilizer and power-head used for CO2 injection. Water was pumped back to the display using a 1/8 th horsepower pump. Originally the majority of the return water went to a spray bar located in the display and the rest was diverted to a slow-flow reverse under gravel filter (RUGF). [Aquatic plant hobbyists have commonly used under gravel heating cables to keep substrate temperatures the same or slightly warmer than the water column. These cables also supplied plant roots with nutrients through convection currents. The slow-flow RUGF was intended to provide the same functions as the heating cables.] It was later determined that the RUGF was not allowing anoxic or anaerobic conditions to occur in the substrate. A process that makes certain nutrients, like iron, more available to plant roots. Flows to the RUGF were shut off and all of the water going to the display went through the spray-bar.

Driftwood And Substrate:
The tank was started with one large driftwood stump as a centerpiece. The driftwood was collected off a local beach and was soaked in fresh water for six weeks to remove salts, prior to being placed in the display tank. This piece of wood was cable-tied to the RUGF plate to keep it submerged. Approximately 300 pounds of Profile’s Turface was added as substrate. Turface is clay-based gravel that is often used as baseball infield material. It has qualities that make it suitable for an aquatic plant display. It is relatively small grained (2-3mm), has a natural look to it, and it has a high cation exchange capacity. The main drawback to the Turface is that it is not as dense as other substrate materials. This makes it "light" under water and doesn’t allow sloping gravel beds and initially plants are easily uprooted. In retrospect I would have used a mixture of Seachem Flourite and 2-3mm river gravel. Another mistake I made with substrate was not adding a few handfuls of peat to the lower half of the substrate when initially setting up the display. The acidic nature of peat makes certain nutrients and dissolved organics available to plant roots.

Carbon Dioxide:
The water column was supplied with carbon dioxide via a compressed gas cylinder. A needle valve was used to limit flow and was set at four to five bubbles per second. During the first three months a Pinpoint pH controller controlled CO2 injection. The pH controller was set to keep the pH between 6.9 and 7.0 (CO2 levels around 20ppm). During these three months the controller failed two times. Once, because of a bad electrode and the second time because the main system completely shut down. Due to the lack of reliability of this controller I decided to bubble the CO2 directly into the system and remove the Pinpoint controller altogether. CO2 flow was set at 3 bubbles per second, which maintained pH near 7.05 when tank lights were on and around 6.9 when the lights were out. Since the water used in the aquarium had a relatively high carbonate hardness value, pH plummet was of little concern.Ideal CO2 levels in a highly lit, planted aquarium should be between 10 and 20ppm. CO2 levels are easy to determine if pH and Carbonate Hardness are known, since there is a direct relationship between the three. An easy to read CO2 chart and explanations are available on the Internet at www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html.

Lighting:
Lighting of the display was accomplished using metal halide fixtures. Originally two 250-watt, 5500K lights were hung 10 inches above the aquarium. As the plants began to grow, the larger ones began to shade to the smaller, foreground growth. Another 250-watt fixture was added. This fixture contained a 6500K Iwasaki bulb and was placed in the center of the tank between the two existing fixtures. The 6500K bulb produced a much "whiter" light that really brought out the colors of the fish and plants. As the plants continued to grow and cover the surface a fourth fixture was added. This contained a 175-watt 5500K bulb.

Nutrients:
Determining nutrient levels proved to be one of the greatest challenges in creating a stable, algae-free environment. I made several mistakes along the way, which resulted in a tank choked by epiphitic green and red algae.

As stated earlier, I began this experiment using a slow-flow RUGF. Even after nutrient dosing, extreme at times, plants still showed signs of deficiencies. Iron levels would drop from 1 ppm to 0 within a few hours. When the RUGF was finally shut off, the need for dosing decreased, nuisance algae disappeared, and the plants began to literally grow out of the display. I believe a couple of things were going on with the use of the RUGF. Potentially, the water flowing up through the substrate from the RUGF was causing nutrients to be oxidized (this is only a theory). Also, the RUGF was not allowing for any anoxic conditions to occur in the substrate. Anoxic conditions make nutrients trapped in the substrate more available to plant roots.

When the plant growth increased dramatically, naturally so did plant density. The density of healthy growing plants is also a factor in creating an algae free environment. Higher plant density leads to a more stable environment.

Measuring nutrient levels proved to be a valuable tool in fine tuning water chemistry specifically for the plants. A mistake I made early on was not measuring for potassium, even though I knew it was a macro nutrient essential for plant growth. It wasn’t until several of my swords showed signs of serious deficiency and growth throughout the tank had stalled, that I sought advice from Steve Dixon, a knowledgeable planted aquarium enthusiast. Steve advised me to order a potassium test kit and begin dosing more potassium nitrate (KNO3). When I raised potassium levels in the display to around 25- ppm, growth picked back up.

Nitrate tended to be deficient in my system as well, even after the heavy feeding the discus required. The KNO3 used to raise potassium levels also raised nitrate. Ideal nitrate levels were between 3-5 ppm.

Phosphate was also measured regularly. Ideally PO4 levels should have remained as close to 0 as possible. At the point when algae be came a problem, phosphate levels reached 1 ppm. Once the plants began thriving (after potassium addition and shut off of RUGF) phosphate levels dropped off to nearly undetectable levels (<0.1 ppm). The plants were utilizing the phosphates quicker than they were introduced to the water column. With a steady decline in PO4, the nuisence algae disappeared from the system.

The fourth nutrient measured was iron. Iron levels were used to gauge the need for iron as well as trace element addition. Iron was measured accurately in our water quality lab on a weekly basis, which allowed me to maintain only a trace in the water column. Throughout the experiment iron levels never rose above 0.08ppm and regularly stayed below 0.02ppm. On a daily basis I used a quick test to determine whether or not iron was present. If the test showed iron in the water column I would hold off dosing until the test read 0. When iron did read 0, I would dose both Seachem Flourish Iron and Seachem Flourish (a trace element solution) following amounts recommended on the bottles. This technique proved to be effective in supplying plants both iron and trace elements in the water column. Once I shut off the RUGF and anaerobic conditions developed in the soil, iron became available to the roots as well, and the water column required less frequent additions of the Seachem fertilizers. Substrate fertilizers were placed directly under sword plants every month to 2 months. Under most plants I would use ½ of a "Jobe’s fertilizer stick for lush palm and ferns". This stick was chosen because of its low phosphate content.

Summary:
The main mistake I made was using the RUGF. When this was shut down, dramatic improvements in display quality ensued. It is theorized the anaerobic conditions that subsequently occurred in the substrate made nutrients more available to the plant roots. This in turn gave the plants what they needed to thrive, increasing their density, and utilizing water column nutrients more efficiently. This left little for nuisance algae to utilize, since they rely on water column nutrients. Planted aquariums can make dramatic displays and create natural environments for freshwater fishes. Each aquarium is different due to the number of variables inherent in such a system. If sufficient lighting is supplied, CO2 is made available, the right substrate is provided, and nutrient levels are managed, an awe-inspiring aquarium can be created.