Coldwater marine aquarium Blog 2008 September
September 21 2008
Symphodus melops

Juvenile corkwing wrasse (Symphodus melops)

Now it is fall and the light levels are dropping rapidly. The temperature is lagging after. The tank has 15 degrees C now. Last year at this time a small, bushy red algae, highly epiphytic and light pink in color appeared. The same phenomenon has happened now. This year there is even more of it. The algae is quite nice. I wonder what is behind this phenomenon. Is it an algae that is there all year, but thrives best under the current light and temperature settings? Is it an algae that occurs in large quantities in the ocean at this time of the year and has been introduced in water that I add to the tank? The coolest would be if it was one of the forms of an algae that is present in the tank all year. Red algae may have several different reproductive stages, some where they are small and hardly visible, some planctonic and some where they appear as large plants.

There is also a very beautiful green algae, most likely a Cladophora sp. This one is also bushy, but softer. It grows in long, branched, strands. I assume it is a summer species and will disappear soon. Hopefully it comes back next year. The mighty growth of coralline algae and sessile animals is continuing. It is only natural since the growth rate is probably exponential. I assume that in a year from now on there won't be a single lit spot that is not covered by coralline algae. Three different species of sea squirts are now reproducing and showing accelerated growth. They practically only grow in the shaded areas, so they are hard to get good pictures of. In addition at least one species of sponge, Halichondria panicea, has spread. The last 2 of my sea hares died recently. I caught 8 or so last winter. They seemed to do well and laid enormous amounts of eggs. Still they gradually disappeared. I wondered what the cause could be. I actually found the cause after some googling. They have a life span of one year. So old age was probably the cause! I hope I can find some young ones this fall.


A fresh year class of gobies has arrived and the water next to the shore line is swarming with them. I have added quite a few painted gobies and some two spotted gobies. The method of catching them is simple. Sit down on the rock next to the water and stir it a little with a small aquarium net. The gobies come swarming. You see, they are attracted to what they see as a large animal eating in the tidal zone. When such animals, like crabs, birds and wolf fish eat they release pieces for the gobies to take.


I haven't succeeded with pipefish so far. All previous specimens have disappeared within short time. I think the two last ones died from some kind of disease. I have always suspected that the conditions for pipefish aren't optimal in the tank, especially for the species that are adapted to calmer waters. Still, some species can also handle more wavy environments and these should have a better chance. The snake pipefish (Entelurus aequorus) that I have added lately have all been found in relatively wave exposed locations. The only thing I can think of is if they are dependent on free swimming plankton passing just in front of they snouts to stimulate feeding. There is none of that in the tank. However if they can move around a little and catch small crustacean and worms crawling around in the bush then there is a lot of food available. I just added the large specimen on the picture. I'll watch it carefully and see if it gets skinny. In that case it goes back in the ocean.


The project with carbon stalled a bit. I ordered carbon and a large reactor from in Germany. After 7 weeks I still hadn't heard anything from them. So I cancelled the order. I have generally had a good impression with that shop, but in the end what counts is the ability to deliver. Anyway, it was kind of lucky for me since I have read, and tested, that carbon isn't all that efficient against miscoloring anyway. The next step now is to try out ozone instead.

At first I was sceptical to ozone. I was worried about the dangers of using this very oxidizing material. Deltec's pages, for example, mention that ozone can "literally strip the skin off your fish". Scary. Ozone in the air is toxic to humans, and should be avoided. Still, after reading Randy Holmes-Farley's excellent articles about ozone in Reefkeeping magazine the picture is slightly different. For example, to sterilize water you need concentrations that are more than 20 times the ones used in aquarium settings and the contact time must be long, perhaps over an hour. In an aquarium setting we are talking about a few seconds with concentrations that barely affect bacteria. Tests had shown that bacterial concentrations did not change in water passing through an ozone reactor. The the question changed from "Is it too strong?" to "Does it do anything at all?". According to Randy Holmes-Farley coloring agents are particularly vulnerable to ozone because of their double carbon molecule bindings. So ozone will target them specifically. That gives some hope. I ordered a redox monitor from Marine Depot in California and received it after a few days. The ozone generator ordered on the same day, from a Norwegian company, and that was supposed to be in stock, still hasn't been shipped after almost 4 weeks.


I cleaned my skimmer recently. Now I found out what kind of environment the barnacles need to grow and prosper. Both the skimmer body itself and the tubing were full of large thriving barnacles. The barnacles in the skimmer body preferred the upper and most turbulent part. The conclusion must be that the type of tank that I have is not suited for this barnacle species (Semibalanus balanoides). They need a much more high energy and turbulent environment. Still, it is very nice to see that there is quite a lot of food for this kind of filter feeder in the tank. There are other barnacle species adapted to deeper calmer waters. But it is unlikely that I will be able to find and identify any larvae of those.

Anapagurus chiroacanthus

To my surprise I found that one of my hermit crabs was of a different species than the rest. This ia a hairy hermit crab (Anapagurus chiroacanthus).

Palaemon adspersus

Palaemon adspersus. Shore prawn.

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