May 1 2011
The last month has been very intense. I've filled the tanks, tuned in the equipment, had my first algae bloom, my first algae crash, found sand and various animals. I have measured water parameters, counted algae cells and looked in the microscope until my eye got big and wet. All the fun and stress with a new aquarium setup. I really hope May will be a bit slower!
I did the water filling in the first weekend in April. The natural seawater was collected at a location in the islands to the west of Bergen. It was a bit long way to drive, but then I was sure to get water with 31 ppt salinity. I got the water in 5 containers of 25 and liters each. It took two trips to get enough water. The water in the refugium turned white hazy after in the first 24 hours after filling. The first week this phenomenon increased. After a few days I could observe small, round algae cells. But since I was inexperienced with the microscope I did not feel absolutely sure that they were algae. But then I saw that some of them were swimming, and amazingly fast too. That helped me separate algae from other small specs in the microscope, since I knew that the swimmers were algae.
I had an incident with the sodium silicate that is used as nutrient for diatoms. I tried mixing it into freshwater to see how it worked. No problems there. But when I put it in saltwater a snowstorm formed. I hoped that it would dissolve after awhile, but no. It sank to the bottom in flakes and gave the water a white hazy color. Also, the Seachem has a dark color thanks to the large amounts of iron. It tended to darken the water slightly, so I decided to use F/8 medium instead, only half the dose. So the next day I emptied the system and took two new trips to the ocean to get water. I found out that the key to using sodium silicate solution was to thin it out with freshwater to 1/1000 of the original concentration, and then add this to the aquarium. No problems after that.
After about one week it was clear that there was an algae bloom in the refugium. In my microscope I could now see beautiful chains of diatoms. They were often 30 cells long. I assumed that this was Skeletonema costatum. The cell sizes depended on where in the life stage they were, but I think about 5 to 15 micrometers in the longest direction. After 8 days I estimated the population of these cells to be about 160 million per liter, and other algae cells roughly 40 million per liter. Unfortunately my equipment isn't really reliable at concentrations below 50 million per liter. So I can only count concentrations that are very high compared to nature. Then again, I need very high concentrations to feed the display tank properly, so low concentrations aren't that interesting anyway. After nearly two weeks I counted 500 million cells per liter of diatoms, the water in the refugium now had a nice red brown color. One of the things I noticed was that the display tank got pretty murky. It seemed like the skimmer was unable to efficiently remove the algae from the water. It took out some, but not nearly enough. I adjusted the flow through the skimmer up, but it did not help much. I counted cell concentrations of 150 million in the display tank. This of course helped the bloom because algae were allowed to return to the refugium an continue multiplying. I hope this is a diatom problem, perhaps smaller non-colonial algae will be easier to skim out.
The water quickly started to cloud.
The plastic trays quickly proved their worth. About once a week I take them out and wash them. It dampens the competition from benthic algae a lot.
Refugium without trays.
After 8 days.
After 11 days. This is what about 500 million diatom cells per liter looks like.
The skimmer had problems with keeping the display tank clean, giving 150 million cells per liter in the display tank. Clearly too much to be aesthetically pleasing.
Diatoms (Skeletonema costatum) under the microscope. This picture is taken with my Canon EOS350D.
Diatoms (Skeletonema costatum). Taken with Bresser microscope camera.
After two weeks there was a crash in the diatom bloom. I don't know what caused it, but I was busy at the time and couldn't measure parameters exactly at the crash. But after the crash phosphate was 0, but Nitrate was not. So it could be phosphate. It may be something wrong with my nitrate test of course. The phosphate test seemed to be good in the calibration check I did. I haven't done a similar calibration on the nitrate test yet. During the bloom I added CO2 and when the crash came pH sank drastically. A pH controller may be more or less required in this type of refugium.
After 2 weeks.
When the crash happened the pH dropped very fast because I didn't reduce the CO2 input. This strongly speaks in favour of using a pH controller.
In Easter I used the holidays to get some sand and animals for the display tank. I got live crushed shell sand from a shallow area. It makes a 2 cm deep sandbed. Its function is both aesthetics and filtration. Of clams I got I got common mussels (Mytilus edulis), horse mussels (Modiolus modiolus ), cockles (Cerastoderma edule), scallops (Mimachlamys varia). I measured the size of all of them so that i can see if they have grown later. I also got some sea squirts that I think are Ascidia mentula, some sponges, barnacles, and a few tiny colonies of dead man's fingers coral (Alcyonium digitatum). On some of the rocks there are hydroids, most notably something that looks like Tubularia indivisa
Common mussel (Mytilus edulis)
Cockles (Cerastoderma edule).
Various animals: 2 horse mussels (Modiolus modiolus), one covered with sponge. 2 Scallops (Mimachlamys varia). 4 sea squirts (Ascidia mentula). And some tiny anemones, worms, barnacles and others on the rocks.
In the short term I hope to continue with growing diatoms and perhaps test out techniques to bring more stability to the refugium population. Alternatively, finding other types of algae to grow and keep stable. More long term I am considering doing an experiement with zooplankton. I am not thinking about growing them by making them reproduce in the refugium, but by dosing artemia eggs into the refugium I may be able to greate a steady flow of enriched artemia. If that works then I will have a method for producing both phyto- and zooplankton. I could then expand my display tank fauna with anemones, soft corals and other zooplankton eating creaures. But that is some time ahead. Right now patience is important.