Coldwater marine aquarium Blog 2008 May
May 14 2008

Time goes so fast now that I find it hard even to keep monthly updates to this blog. Work is very demanding, as always, and in my spare time I have projects too. Originally I was thinking of making several updates a month, but for the most I have barely managed once a month. I don't really think that is going to change for the better, but I hope to keep it up at the current frequency.

Anyway, in nature the spring bloom of algae has come, and maybe even gone, in April. The water is now thick with zooplankton. All macro algae are growing greatly at this time too. Where it was possible to see the bottom before there is a thick canopy of large kelp leaves and epiphytes. The beaches are full of rotting vegetation and plankton. Searching among the rocks at low tide can actually be a bit disgusting because of the smell. I have found rock pools that were had a layer of about a centimeter of rotting animals at the bottom. I won't say anything about the water quality in those ponds. All inhabitans seemed dying or decomposing.


Semibalanus balanoides

This is the biggest swarm of barnacle larvae I got. When the wave generator was off they converged on a point on the surface and formed this strange vortex.

The great yearly barnacle spawning is over. I wasn't as successful as hoped in getting barnacle larvare to settle in my tank. The orignal idea was to get thousands to settle on the walls and rocks. Still, I tried and got a few dozen in various places. I learned a lot about barnacle larvae. I thought that they were kind of stupid and just swam around in the water until they hit an object, then settled on it no matter what or where it was. Not so at all. They actively search for a spot and have quite strict demands when it comes to the quality of the location. The reason the rocks are completely pink colored by them in some places is that those places have all the right properties. Barnacle larvae can swim and crawl around a long time before decideing to settle on a spot. In the tank the overflow was of course very tempting for most of them. That meant they got caught in the mechanical filter there. Some got through to the sump. They settled around the tube that comes from the overflow. It will be interesting to see if they survive and grow. Some even settled on the wall inside the skimmer! But who can blame them, it is a nice turbulent area right? Anyway, I think those who are in the tank should have a good chance. They all settled in places with high flow. The posthorn worms are doing fine and they probably take the same food as small barnacles. Also, my large barnacles seem to do well.

Semibalanus balanoides

Barnacle larvae (Semibalanus balanoides)


Various algae

Bladder wrack (Fucus vesiculosus) with epiphytes, and many others.

Lots has happened here lately. Last month I tried to introduce some nice looking reds of the species Phycodrys rubens and/or Delesseria sanguinea, but all speciemens have crumbled into nothing. I don't know if that is some seasonal variation or environmental adaption (probably not) or if they simply don't get good conditions in the tank. We'll see if I experiment some more with them later. Another algae that has surprised me in a negative way is the Ulva lactuca. It has successfully spread to many spots in the tank and is popping up. For a while there were 20 long leaves growing. But now it is gone. That is, small leaves of one or two centimeters in height are still holding out here and there. But the large ones are gone and don't seem to be returning. I wonder what the reason is. It could be that the sea hares are simply grazing them down. The sea hares are very active and efficient grazers, though they don't scrape the rock clean. They just eat off the tops.

Various algae

Ascophyllum nodosum. A very common, large and slow growing intertidal brown algae. The local name translates to "pig wrack", because people used to feed the livestock with them. The epiphytes were cleaned off by the sea hares after a day or two.

There are two very common types of intertidal brown algae around here: The bladder wrack (Fucus vesiculosus) and knotted wrack (Ascophyllum nodosum). These are large, slow growing, and often form forests on the shore in more sheltered areas where the kelps don't grow. I have always wanted these in the tank, but I have heard that they are dependent on being laid dry by tides to avoid being smothered by epiphytes. I've also assumed that since they vere so slow growing they would get smothered anyway. But now I've tried bladder wrack since winter and they are really growing well. Only one specimen has serious epiphyte problems and even this one is growing very well and has developed bladders. So I am getting bolder. I have even introduced my first large specimen of knotted wrack. It would be great to have a small forest of these as they harbour so many other organisms. They would probably fit better in the tank than kelp. I am even considering completely removing the Laminaria kelp specimens. They are very dominating, and I suspect them of coloring the water brown. I have a miscoloration problem. Perhaps it would be better with less kelp. I am not so afraid of fast growing brown thread anymore. I know I have plenty of other algae to compete with them.

Another nice addition is the brown that you can see behind the large kelp leaf in the first picture above. This one is spreading around in the tank. I grows and really seems to enjoy itself. No success at an id yet. But I think it is a summer algae, that is, it has a heteromorphic growth cycle (think that's the name). It dies in fall, but the spores it has released winters over as a small crust on rocs. These crusts release new spores in spring that settle and become large growths again.

I also have a specimen of Sargassum muticum. It grows rapidly. It is the light brown long algae with bladders growing all the way to the surface. It is a species that is relatively newly introduced to the flora here. It probably came with ballast water from the Pacific.

Finally, specimens that I think are Scytosiphon lomentaria are popping up everywhere. These are the long strands that you can see on various pictures. They are mostly on rocks that were not live from the ocean. So these must have spread and settled by themselves in the tank. That is really great!

Sea hare spawn?

Red algae

In the algae here you can see some small orange blobs. I suspect thay are sea hares or some other small snail spawn.

Lately I've noticed the algae is crawling with one or two millimeters long bright orange blobs. They could be worms, but remind me of small slugs. I wonder if they could be sea hares. The sea hares are mating constantly and laying enormous amounts of eggs everywhere. I've read that the larvae are pelagic so I didn't expect them to survie, but it could be that some have responded to contact with the right types of algae and settled.

Plankton time

As said the ocean is very rich in zooplankton now. In some locations, with the right current or wind conditions, the concentrations can be enormous. I was really lucky and was able come across a great spot and catch about 600 grams of mainly Calanus finmarchicus copepods. But various others, like barnacles, too. It made almost 3 ice cube trays of food. I let the water flow off before putting them in the jar at the location. I believe that preserves them better. The norvegian name for Calanus finmarchicus is "rauåte" which means "red food". Food for fish that is. One of very few such small animals that have common names. They have a distinct red or pinkish color. They are some of the most important animals in the oceanic food webs in the Norwegian sea and the North sea.

Clams dying

I've always wondered how the clams in the system are doing. There were lots of clams in the live sand when I started the tank. In the beginning I could see their siphons coming up everywhere. Then they disappeared after a few months. I assumed they were dead. This spring however, many clams have died in a visible way. Dead clams have become visble on the surface of the the sandbed. That hasn't happened before. But the stangest phenomenon, that hasn't occured before, is that they come up and just lie on top of the sand. After a few weeks like that they die. That has happened several times this spring. I wonder why some many clams died in just this period. I am also very curious about the xxx. Quite a few of them have died in the last year, but many still live. I wonder what the food situation is. Is the lots of food or is there barely enough for some of them to stay alive? The diet balance must be unnatural to them. In nature they eat a lot of phyto plancton. In the tank they have bacteria, small pieces of algae, algae spores, detritus and the food i feed directly. I should have marked some to study growth, and comapred that to data on natural growth rates. That could give an indicator on the diet situation.

Small crustaceans

Here are some of the animals that the tank is crawling with right now. These were found in a clump of hair algae. The one in the two first pictures is a little less than a millimeter in length. I have no idea of the classification. The last one is much smaller, only a fifth of a millimeter, and is presumably in the harpacticoida order.

Alcyonium digitatum

Dead man's fingers (Alcyonium digitatum)


Can you see a crab in this picture? It is a spider or lyre crab. Perhaps Hyas sp.

Archidoris pseudoargus

Sea lemons (Archidoris pseudoargus) mating. Would like to have these in the tank, but like with most nudibranchs I don't have enough food. They eat the sponge you see on the rock.

Littorina littorea

These snails feed on something that is related to the decomposing algae being washed ashore on this location.

Pholis gunnellus

Here is one of my rock eels (Pholis gunnellus). They are getting tamer so better pictures will follow.

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