November 17 2013
In mid September I decided to empty the aquariums and finish the plankton project. It had been running for almost two and a half years, which is much more than planned to begin with. It has been a very successful project even though many of the things I tried didn't work out. But the main thing, which was to grow phytoplakton and to feed animals with it worked very well. So I am pleased with the result. All the animals, including the live sand and rocks were transported back to the ocean in good shape.
Animals ready for transport. The big ribbon worm made it too, though you can't see it in the picture. I didn't bother to measure it.
The most successful animals in the aquarium were the blue mussels (Mytilus edulis). They grew like weed. I only put a few ones in there and by the end there were about 150 at 2 cm or more, plus a great number of smaller ones from this year. The combined wet weight was 1.1 kilos, as you can see on the picture below. It is one of the coolest things that have happened to me in the aquarium hobby.
Blue mussels (Mytilus edulis)
All the blue mussels pluss two horse mussels (Modiolus modiolus).
Pretty much all of these grew from larvae to adults in the aquarium.
The sand was pretty much undisturbed by me for more than 2 years. Combined with a heavy bioload, some nice hydrogen sulfide had developed down there.
That black stuff smells bad.
As I mentioned in the last update, in the last months of the project most surfaces in the display tank got covered with something that looked like mud. At close distance one could see that this was animals that lived inside mud tubes. I assumed it was polychaete worms. This was confirmed when I took some samples and looked at them in the microscope.
Here you can see the little worms in mud tubes.
A single worm out of its tube.
Harpacticoid copepod, female with eggs.
When looking in the stereomicroscope I saw an animal that looked like a crustacean, but it moved in a way that reminded me very much of a terresterial mite. I knew mites lived in freshwater so I started wondering if mites lived in saltwater too. After a quick google search it was confirmed that mites live in the ocean. So I assume these are mites.
Mite. Pinkish animal in the middle of the picture.
Mite. I didn't even know they were in the ocean.
The conclusion from this project is, most of all, that it is possible to grow phytoplankton in significant amounts this way. The best proof is that the system could grow 1.1 kilos of mussels and keep them alive, in addition to a significant volume of other animals. In the later months of the project I saw tendencies to nutrient limitation. The clams did not feed as much as before (not as wide open). The same was true for the brittle stars. The water did not have any visible cloudiness to it like in the early days. I think it was simply because the limit on how much the refugium could produce was met. It is a reminder that the biomass in a well functioning filter feeder system will continue to grow until there isn't enough food for more. The challenge is then to make sure that the wanted animals are winning the competition about the food.
I would like to start a new feeding project with zooplankton next. But at the time beeing I don't know when that will be. I have a room in the apartement set off for aquarium projects, so space isn't a problem. The problem is to have the time and money. When I start another project I will post threads on coldwater facebook groups and various forums, so you will find it without having to look at this site all the time. There probably won't be any updates here in the near future.
I want to start scuba diving. My freediving buddy and I are planning to take the PADI open water dive course. He has already taken it about two decades ago, but feel a need to refresh the knownledge. I would really like to take the advanced open water course too as I am interested in seeing what is going on below the photic zone at 30 meters. I can't afford equipment at the moment though, but hopefully some day.
I am interested in refrigeration technology and reading a little about it these days. I am really itching to build a chiller or two that I will need for my zooplankton project. Lets hope the itch stays!