Coldwater marine aquarium Blog 2008 December
December 25 2008

Great spider crab

Hyas araneus

Just after molting.

I was lucky enough to get some pictures of my great spider crab (Hyas araneus) just after it had molted. Now I could see it clearly. After a few days it was covbered with algae from around its favourite hideout.

Hyas araneus

A few days later.

Water quality

Now that the light input is practically nothing there is very little uptake of inorganic nutrients. I just got a nitrate reading of 50 mg/l! What worries me the most is the phosphate concentration that is up to 0.5 mg/l. At this level it is inhibiting to calcification. This can cause harm to many of my animals. I will do some water changes, but they will not have a great effect. I guess I'll just have to hope that things improve rapidly when light returns in February. The two pictures below illustrate water quality improvements after I started using ozone.

Before ozone

Before ozone. Tank water on the left. Tap water on the right.

After ozone

After ozone. I don't know which one is tap water.

Actinia equina

Beadled anemone (Actinia equina)

Hippolyte varians

Chameleon prawn (Hippolyte varians). About 2 cm long.

Sea squirt

This sea squirt may be Ascidiella aspersa.

Sea squirt

This too is probably Ascidiella aspersa.

Macropodia rostrata

Spider crab (Macropodia rostrata).

Sea squirts

The orange thing to the right is a small type of colony forming sea squirts are spreading everywhere in the tank's shaded areas.

Symphodus melops

One of my three juvenile corckwing wrasses (Symphodus melops).

Urticina eques

Dahlia anemone (Urticina eques).


Some hydroid.

Urticina felina

Dahlia anemone (Urticina felina). Hiding in crevice.

Actinia equina

Beadled anemone (Actinia equina). Plumose anemones (Metridium senile) in the background.

Ciona intestinalis

Dahlia anemone (Urticina felina). And a second generation sea squirt (Ciona intestinalis) that has grown into a distinct shape below the large moving kelp specimens.

Red algae

There are still many species of red algae that I would like to have. Some of the nicest species don't seem to thrive in the tank. But I see some evidence of reproduction at least.

Ophiocomina nigra

Black brittle star (Ophiocomina nigra). Filtering the water. Always hiding in the shadows. So I had to use a flash to get a photo.

Galathea squamifera

Squat lobster (Galathea squamifera). Also a flash photo.

Red algae

Some new, beautiful reds. Hope they make it.


A chiton.

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