Reef Tank: Diatoms

Last night I noticed a golden-brown colored dust growing on the substrate and rocks. I spent some time searching for algae species identification charts, and eventually came across an About.com article regarding diatoms. A trip to Wikipedia and some other resources confirmed that was what I had most likely observed in my tank. Of particular interest to me was this section from About:

This type of algae outbreak typically occurs when a tank is just completing or has finished the nitrogen cycling process, new live rock is introduced, as the curing process can add nutrients when some organisms on the rock dies off, or tank maintenance has been neglected.

Obviously that would pertain to current events in my reef tank. I had assumed that ammonia levels, which had been as high as 8ppm three days earlier, would require at least another week to subside, and had resolved not to waste my time and test kits checking it every day. The growth of diatoms and subsequent information about them forced a change of mind, and I conducted my usual tests this evening with surprising results: ammonia had indeed dropped to somewhere between 0.25 and 0ppm, an impressive down swing from the levels recorded on Sunday. Nitrite and Nitrate were still high, but that would be expected as they are the products of processed ammonia.

Also of interest was this summary of diatoms and their use of silicates, found in the Wikipedia article:

Diatoms cells are contained within a unique silicate (silicic acid) cell wall comprised of two separate valves (or shells). The biogenic silica that the cell wall is composed of is synthesised intracellularly by the polymerisation of silicic acid monomers. This material is then extruded to the cell exterior and added to the wall. Diatom cell walls are also called frustules or tests, and their two valves typically overlap one other like the two halves of a petri dish. In most species, when a diatom divides to produce two daughter cells, each cell keeps one of the two valves and grows a smaller valve within it. As a result, after each division cycle the average size of diatom cells in the population gets smaller. Once such cells reach a certain minimum size, rather than simply divide vegetatively, they reverse this decline by forming an auxospore. This expands in size to give rise to a much larger cell, which then returns to size-diminishing divisions. Auxospore production is almost always linked to meiosis and sexual reproduction.

Once again, an insightful article from Randy Holmes-Farley helps to clarify both the cause and effect. As mentioned above, diatoms construct their cell wall from silicate, hence their presence could be considered an indicator of silicates being present in the aquarium. His article discusses how silica occurs in the ocean and in the aquarium, as well as what organisms use it and how it can be controlled and dosed. Great stuff.

My assumption is that there would be a high level of silicates found in my tank due to a number of recent inputs:
• Unfiltered tap water for the initial tank fill
• Sand and sediment on the live rock
• Live sand substrate

So there should be plenty of raw material for diatoms, in addition to the high levels of light for photosynthesis (I've been running the tank lights 8 hours a day) and nitrate for fertilizer. Conventional wisdom seems to indicate that after the initial outbreak of diatoms in a new aquarium one can expect green algae to replace it. My initial hobbyist panic response to seeing my pristine new white sand bed polluted with some form of new algae has since been replaced with curiosity now that I've learned about the circumstances under which it appears. I intend to see if I can get a sample out of the tank and take a look under the microscope this evening, as the imagery on Wikipedia is quite stunning.

Todays Parameters:
Temperature: 81F
Specific Gravity: 1.026
pH: 7.9
Ammonia: .025ppm*
Nitrite: 5ppm
Nitrate: 10ppm

* The color of the ammonia test was actually somewhere between 0.25ppm and 0ppm, and closer to 0. In the interest of caution I am rounding up on the chart.

Links from this post:
Randy's article in Advanced Aquarist about silica and diatoms:
http://www.advancedaquarist.com/issues/jan2003/feature.htm

Wikipedia article on diatoms:
http://en.wikipedia.org/wiki/Diatoms

About.com article on diatoms:
http://saltaquarium.about.com/cs/algaecontrol/a/aa091100.htm

Chemistry: The Nitrogen Cycle

As mentioned previously, my reef tank is currently going through a startup phase in which the nitrogen cycle becomes established. As there isn't much for me to do until this phase completes itself, I decided to dig a little deeper on the chemistry of this cycle and how it specifically relates to reef aquaria.

Fortunately for those of us who spent too much time goofing around in high school chemistry, there are a number of talented professionals contributing to the knowledge base. Of particular note is Randy Holmes-Farley, a chemist at Genzyme (which just so happens to be down the street from where I work). He writes articles for several online reef aquaria journals, and this morning I enjoyed reading two on the nitrogen cycle: Nitrite and the Reef Aquarium and Nitrate in the Reef Aquarium.

Of specific interest in these articles were a few points that differ in marine aquaria from freshwater systems, and that also defy what is passed along in forums as conventional wisdom. For one thing, it appears that in saltwater systems nitrites are not considered highly toxic unlike in freshwater tanks where they are considered as deadly as ammonia. Randy also lists out proven methods of eliminating nitrates in the reef tank, which though also not considered highly toxic, can be contributors to nuisance algae. Both articles are a great read for those looking to get an introduction to these steps in the nitrogen cycle.

Reef Tank: The Cycle Begins

Once live rock has been introduced into a new aquarium the waiting game begins. Live rock brings with it life of all forms, from simple bacteria and algae cells up to more advanced life forms like sponges, worms and even coral polyps. Naturally on the long journey from the South Pacific (specifically, Tonga) much of this life perished. The combination of live and dead organisms helps to jump start the nitrogen cycle. Reef Central has a good FAQ regarding the nitrogen cycle as it pertains to reef aquariums.

In short, dead organisms arriving on the live rock decay, creating ammonia which is toxic to all life and probably killing off other organisms that had managed to survive the trip. Fortunately bacteria present in the rock are capable of converting ammonia to nitrite (still toxic to marine life) and then converting it further to nitrate (somewhat toxic at higher levels, but not as bad as the other two). As the patient new aquarist, I must sit back and watch this cycle slowly take place over the next two to six weeks, watching via test kits as the levels of ammonia, nitrite and nitrate change in the aquarium. Once the bacteria has taken hold ammonia and nitrite levels should read at 0 ppm. Nitrate may still show up in minute levels and can be minimized via water changes.

I plan on testing the parameters every four days or so to monitor this cycle, and to perform 20% water changes once a week to further reduce toxins. As a sign of a successful cycle beginning, we're looking for a drop in ammonia and a rise in nitrate to indicate the bacteria are at work. The protein skimmer has been pulling out some very light skinmate but doesn't appear to be quite as dialed in as I would like. I'm not sure if this is related to a lack of nutrients in the water to be skimmed or some other variable.

Todays Parameters:
Specific Gravity: 1.0255
pH: 7.9
Ammonia: 8ppm
Nitrite: 5ppm
Nitrate: 10ppm

Reef Tank: Live Rock Arrives

Today my order of live rock arrived from Live Aquaria, bringing the first real look of a reef to this tank, along with a multitude of life. I had chosen 30 pounds of Lala Select rock harvested in Tonga which has a unique look and coloration. I wanted something different from the pink Fiji rock that is nearly ubiquitous in the modern reef aquarium. This rock did not disappoint, the colors of the encrusting corraline algae were unique and beautiful:



The design I had sketched out on vacation (with a snorkel trip still fresh in my mind) called for creating a slanted pile of rocks from the left side of the aquarium with an isolated island of one rock set to the right. The isolated rock concept was directly influenced by invincible569's 300 gallon system that I had been following on Reef Central for some time. Laying out a reef aquarium design is not easy: I had absolutely no idea what the size or shape of the rocks would be as they were coming via mail order.



I took all the rocks out and set them up on the kitchen table where I had marked off the dimensions of the aquarium, and attempted to reconstruct the design. Although the rocks were much larger than I had anticipated (the 30lbs was primarily comprised of only three large rocks), I was able to come closed than I anticipated to the original design. One rock in particular was well suited to become the solitary island, while the other two fit together nicely to create a larger area complete with cave and peaks.



I snapped enough photos that I could remember how things had been placed, and then dunked each piece of rock in salt water to remove sand and other loose debris before reconstructing the arrangement in the aquarium. Although the left side isn't quite as high as I had originally sketched out, I am quite pleased with the final results. As someone pointed out after the fact, its important to leave room for the corals to grow in. Creating a natural scene in a smaller aquarium can be tough with large rocks, and I'd seen enough poor examples to know both what I wanted to do and what I wanted to avoid.



Now the long wait while life dies off, bacteria becomes established and the tank becomes habitable. Plenty of time to research coral species and get some real world experience with the alchemy of creating and changing salt water.

Snorkeling: Some Snapshots from Vacation

Cassie and I had a great time in the Dominican. There really isn't any way to have a bad time as far as I can tell. We did some snorkeling on an inner lagoon reef and saw some great stuff. Lots of soft corals, some brain coral, and a few leathers. Tons of fish of course. I came away with some great ideas for how to layout my future reef project and some awesome visuals of what a reef looks like in nature.

I don't have an underwater camera, so these surface shots of my ugly head are all there is.