Sunday, November 11, 2007

Diatoms: What's all that brown crap?


My tank has been up for a week now and just a day ago I started noticing patches of brown algae on one of my live rocks and parts of the sand. These brown patches are diatoms which are one of the most common types of phytoplankton found in marine habitats. Although diatoms are generally not a good sign in an established tank, they are part of the nitrogen cycle and their presence in a new tank can signify that the cycle is moving along. Several things can trigger a diatom bloom: high levels of nitrate, significant amounts of phosphate among many others. I dismissed phosphate as a possible cause as I've been diligently using reverse osmosis water for top offs. This could only mean high levels of nitrate in my tank which means ammonia and nitrite levels have dropped down to zero (or pretty close to zero) and my tank is nearing the end of its cycle! Or so I thought.

The Lying, Cheating Test Kit

So I ran the scheduled water test today and expected to see some new results. Zero levels of ammonia, zero levels of nitrite and a high level of nitrate which could possibly explain my diatom bloom. Instead I'm getting the same readings all across the board!

So I ran out and picked up a different test kit. This time I got the Reef Master Test Kit by API. This test kit has testers for everything important you need to know in a reef aquarium: carbonate hardness, calcium, phosphate and nitrate, but not ammonia and nitrite. There's another test kit called Saltwater Master Test Kit that has testers for ammonia and nitrite, but not calcium and phosphate. I figure as my tank matures, I'll be using the Reef Master Test kit more and more so I opted for this instead.

As I mentioned earlier, test readings with the Red Sea Marine Lab came out with the same readings as the last one. The Reef Master Test Kit on the other hand came out with an entirely different nitrate reading, which is the only test I can compare between the two kits. While Red Sea Marine Lab reported a nitrate reading of 5.0 ppm on both tests, the Saltwater Master Test Kit reported a nitrate reading of 10 ppm—twice more than the first kit. This level of nitrate explains my diatom bloom.

Top view of the diatom bloom:


This threw me off completely so for now on, I'm sticking with the testers by API and could probably end up banning Red Sea's testers altogether after I do some more comparison tests. The Reef Master Test Kit also reported the following readings:

  • Alkalinity: 12 dKH
  • Calcium: 500 mg/L
  • Phosphate: 0

The calcium reading is at a normal level and the phosphate result is a relief and again helps to point the diatom bloom back to high nitrate levels. In any case, this calls for my scheduled and probably much needed water change.

So I did a 10% water change and hopefully this will improve water parameters in the next week. I also cleaned out the media in the power filter and rinsed them with reverse osmosis water.

Mod of the Week


I added the first extra equipment in the tank aside from the heater. I've always felt that the stock filter that came with the tank might not be able to provide any circulation as it only circulates water at 40 gph. I added a Rio 50 powerhead which circulates water at 60 gph. The powerhead is tiny at 2.2" x 1.4" x 1.8" which is perfect for a nano tank. This added water flow gives the tank a combined circulation of 100 gph which means the whole tank is recirculated 33 times in an hour. Hopefully this provides enough circulation for the tank without producing too much flow for some of the corals that I plan to add later that require very little flow.

My expenses this week:

  • Rio 50 Powerhead: $15.00
  • API Reef Master Test Kit: $30.00
  • (6) 1 gallon bottles of purified water: $6.00
  • 1 bag Oceanic Natural Sea Salt Mix: $4.00 (for making a fresh batch of saltwater)

1 comment:

  1. Thanks for the post! My experience mirrors yours, so it's been very helpful.

    ReplyDelete