February 1 2012

Just a small update

January was another month dedicated to the copepod project. I kept the temperature at between 12 and 14 C. I added copepods in several different batches, from various local areas. Incredibly enough I managed to do another mysis mistake. I added a large catch of small mysids that were probably in the genus Hemimysis. I have seen and caught these many times before, always being convinced they were krills. It was kind of embarrassing to find out that even if they had been krill that wouldn't have helped much. Northern krill is also a predator. Actually it is more likely that the mysids are less predatory than krill. The Hemimysis species seem to be omnivores from what I have read. So I am taking the chance that they are not a problem to keep with the copepods. Besides the calanoid copepods I also saw some with shorter antennae. They may be cyclopoids. Anyway, by the end of the month I couldn't observe any free swimming animals in the refugium. They seem to disappear after a few days, just like before. How it happens is still a mystery to me. But the benthic harpactoids are starting to multiply in large numbers again. Funny that they seem to love the environment in the refugium while the other ones don't. I will keep this setup going in the coming months. I hope the harpactiods will amount to something. I will probably add other pods regularly.


The water soon gets rather brown in the display tank. That could of course be because of plankton concentration, but I have a feeling that it has to do with DOC, dissolved organic carbon. So I decided to fire up my old favourite, the ozone system, again. The simplest thing with ozone is to generate it, but adding it safely to tank water presents a number of flow related challenges. But finally I managed to solve all the issues with input air, output air and output water. I needed to move the skimmer higher and restrict the input water flow quite a bit. I had an unused RedOx probe from my last project that I calibrated and used. The water coloring immediately disappeared. I plan to add enough ozone to keep the redox closer to 300 than the original 200 before I started adding ozone. I am curious about any effect it can have on filter feeders or algae growth.

Brown water

The can to the right contains water tapped from the display tank. The one to the left has water fresh from the ocean. The difference is obvious.

Ozone generator setup

The pipes on top of the chiller contain carbon to filter exit air. In the end of the return pipe there is a net and some carbon.

Ozone generator RedOx monitor

The ozone generator and RedOx monitor. As you can see my ORP level was less than 200 mV when I started. That is low.


I have been freediving a few times in January and found some Henricia starfish that I added to the tank. They seem to do well so far, but I don't like their interest in the few sponges I have. I read something about this on the net and found that researchers had observed the behaviour of sitting on sponges, but it was not known if they were eating the sponges or just using the flow around them.

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