sea gherkin

Another ‘lifer’ yesterday: a Sea gherkin Pawsonia saxicola, at Castle Beach in Falmouth. It is a small sea cucumber (a relative of the Cushion star next to it); a very cool find indeed!

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The main aim though was to collect more snails to help out in the grazing project. This was pretty easy of course. I collected a couple more Painted top shells Calliostoma zizyphinum and many, mainly juvenile, Grey top shells Gibbula umbilicalis. I also picked up a beautiful small Spiny starfish Marthasterias glacialis; this fellow will go after the snails but as long as the predation is not too severe that will be OK, let’s see. Finally, using my little aquarium net, I went after some fish high up the shore and caught a tiny Two-spotted goby Gobiusculus flavescens. I need to catch a bunch more of those, hope to post about that soon

aquarium update: snails

Time for an update. The five Snakelocks anemones have settled and are doing very well (I have fed them some defrosted shrimps which they quickly devour). The Leach’s spider crab was sitting happily under one of the anemones until it decided to move behind a piece of slate and now does not show itself much anymore. Perhaps this has to do with a prawn I introduced, although I have not seen any scuffles. I have to see what I’ll do about this. If it is really shy then I perhaps have to choose between keeping it or introducing fish. In any case I have seen it munching on some algae and a dead Cushion star and it seems to do OK.

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The main problem I have is the dreaded return of algae…There is quite a diversity of them: fuzzy green ones, darker green blotches, slimy purple ones, brown diatoms and more. All interesting organisms surely but I do not want them to take over the tank! I have used food sparingly and used the skimmer most nights, but now have also removed my daylight lamp, to leave a single actinic lamp (see this post about lighting). I still have to get used to this new look, but less light must surely help. Most interestingly, I have enlisted the help of 80 or so grazing snails. Mainly the Common periwinkle Littorina littorea and the Flat top shell Gibbula umbilicalis but also some other species, including two very small Painted top shells Calliostoma zizyphimum. I never had many snails in my aquarium, as they were always eaten by Shannies, but hopefully they will survive this time. I will dunk in a lot more snails, and keep an eye out which species does best. A Flat top shell (picture taken using my olloclip macrolens for the iPhone):

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One returning encrusting red algae is actually a seaweed, with new ‘leaves’ growing from the round crusts. I suspect it is Devil’s tongue weed Grateloupia turuturu. I have been scraping it off the glass, except from the corners where the scraper is of no use, but will let the rest sit and see how it grows:

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I also noticed that Sea lettuce Ulva has started to grow from the slate. The aquarium does not look that nice yet, but with the new animals there is plenty to watch in any case!