March 11 2012

Coldwater marine aquarium
Coldwater marine aquarium

The refugium has now been running for more than two months without a restart, and it is still just as clean as in the beginning. It has been producing algae at a good rate most of the time. When it comes to zooplankters, like calanoid copepods, there hasn't been any progress, and I actually decided to give it up at the start of February. I decided to see if it is possible to get such concentrations of benthic animals in the refugium that it functions as a zooplankton input. There is a problem with this: While I can measure the amount of benthic animals that flow into the display tank, I don't know how many of them that are available as food. They may just swim to the bottom and never be eaten by the filter feeders. Still, with many enough it could work. At the moment there are 3 species of semi benthic animals in the refugium: Harpacticoid copepods, mysids and a type of amphipods. I think the mysids have reproduced, but I am not sure. They don't occur in great concentrations. The amphipods have clearly reproduced. But their numbers are not great either. Only the copepods have truly bloomed. But I am not sure if the bloom was large enough. Also, I don't know if the bloom was fueled by algae growing on the walls or planktic algae. The bloom died off at the end of February. At the same time I observed a phytoplankton bloom.

Ozone incident

Ozone is dangerous and a pain to use. But it is so worth it in an aquarium like this. I had an incident early last month. I thought I was on the safe side when adding ozone because the RedOx was well below 300, and 400 is the recommended value for reef tanks. But one morning, after the RedOx had risen a lot during the night, I noticed that all the brittle stars were simply gone. When I looked closer i saw that they were all desperately trying to hide under rocks. Some seemed to be dead. I pulled out the plug on the ozone generator and started the refugium pump to add some biomass the display tank. Later in the day the situation went back to normal, but it sure was a close call.

Ozone incident

It was early morning and I didn't have time to take a good picture. But here you can see that all the brittle stars are gone from view.

Calibration fluid ate my pants(?)

Suddenly one day I discovered some white patches on the front of my pants. I noticed that I could just pick out lagre patches of cloth. The day before I may have splashed some American Marine RedOx calibration fluid on me when I tipped over a small bag of it on the table. I cleaned the table and floor quickly, so no harm there. But I forget the pants and they were ruined.

RedOx calibration fluid on pants

Who ate my pants?

Better lighting

I have kind of given up on keeping the temperature low in the refugium. Low temperature seems to be detrimental to growth. I have been worried that there is too little light. After all, the light energy is the only fuel source for all the life in the whole system. So therefore I bought an extra 24 Watts single tube. I made the existing fixture and the new one into a single unit by using the supplied aluminium parts, a little hole drilling, sawing and a few tiny bolts. The new unit fits perfectly over the refugum. I don't do CO2 dosing now. The nice thing about that is the stability, and the fact that the pH monitor now works almost like a gauge of photsynthesis. At max growth the pH is 8.8 in the refugium. At minimum it drops to 7.5.

Giesemann T5 aquarium lights
Giesemann T5 aquarium lights


I've had lots of hydroids in the display tank all the time. For awhile i thought all the large ones were dead since I only saw the stems and not the polyps themselves. But now it seems like I haven't lost a singe one of them. They are shedding medusae and several medusae are swimming around in the refugium. I even have polyps in the refugium, meaning that there has been actual sexual reproduction. It would be great if some of the larvae from the medusae would actually manage to get back into the displaytank and settle as new polyps there. Now, I cannot be 100% sure there has been actual reproduction in the system since I have introduced plankton to the refugium often, and the larvae could have come that way.

Hydroids in coldwater marine aquarium

These hydroids have lived in the display tank for 11 months and now seem to be producing medusae at a high rate.

Henricia sea stars

My Henricia sea stars were beautiful animals. But I could observe them eating sponges and even small anemones. So I decided to take them out. Sad, but I just can't have something that eats the small and vulnerable filter animals in the system. The black brittle stars are bad enough.

Henricia sea star in coldwater marine aquarium

Pink Henricia sp. sea star.

Some pictures

Dead man's fingers, Alcyonium digitatum

Dead man's fingers (Alcyonium digitatum). These have their polyps out all the time now.

Dead man's fingers, Alcyonium digitatum

Dead man's fingers (Alcyonium digitatum). Notice the stone boring clam inside the colony at the base.

Blue mussels, Mytilus edulis

Blue mussels (Mytilus edulis)

Coldwater marine aquarium

Plans ahead

The spring zooplankton bloom is in full swing here. At the time being I am adding zooplankton all the time. The hope is that some animal will at some point be able to multiply to significant numbers in the refugium.

Back Home