Tag Archives: algae

St. Cuthbert’s Cave

Posted on by under photography, wide angle

Holywell Beach on the North Coast of Cornwall is known for a small sea cave which houses a ‘holy well’. According to Mabel Quiller-Couch, in her 1894 book “Ancient Holy Wells of Cornwall” in 995 AD the bishop of Lindisfarne, Aldhun, was bringing the remains of saint Cuthbert back to Ireland. Blown off course in a gale, he was left stranded in Cornwall where he settled and built a church dedicated to St Cuthbert. After some years however, an oracle instructed Aldhun to return the relics of St Cuthbert to Durham. As he was leaving from Holywell Bay, the saint’s bones touched the side of the well, giving the spring its magical healing powers. In medieval times, many people flocked to this cave to seek out the healing powers of the spring.

I was in the area this week when the tide was low (at high tide the cave is completely flooded, so you have to check the tides!) and decided to bring out the fisheye lens and a tripod to take some long exposure pics. They came out all right. There are more colourful photos available online, but my suspicion is that these use artificial light and sometimes also some enthusiastic post-processing. By using the longest possible exposure time on my camera (Olympus OMD E-M1markII), a full minute, I was able to let enough light into the camera. This enabled me to use f/18, allowing great depth of field, and ISO200, meaning little noise.

The formations result from a rare (in Cornwall) limestone deposit in the roof of the cave. Slightly acidic rainwater percolates through this limestone, dissolving calcite and becoming enriched in calcium bicarbonate. When the water drips down the rocks, the process is reversed and calcite precipitates, especially in areas where the water moves a little, causing CO2 to gas off. This results in the dam-like rimstone (or gours) formations. The tiny ‘rice terrace’-like formations on the dams are called microgours. I’d like to go back one time to experiment more and also to take some macro photos of the microgours and colourful microbes.

aquarium update: snails

Posted on by under algae, anemones, aquarium update, crustaceans, molluscs

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!

new sand

Posted on by under algae, anemones, crustaceans, fish, molluscs, not suitable for the aquarium, planted aquarium, Red Sea Max 130D, seaweeds

Welcome to this most obscure of blogs, my dear reader. The aquarium is a bit of a mess at the moment for a variety of reasons. First of all there are a lot of algae growing; I have a bag with Rowaphos hanging in the back compartment to remove phosphates but this does not seem to help much (I have had good experiences with before though). Second, one of my pumps broke and so filtration runs at half capacity. Third, the mixed success of planting many different seaweeds has left loads of detritus in the tank. I have made large water changes which helped a bit. An additional tank for experimenting would be nice to have… Fourth, I have been unlucky with some of the seaweeds: the Wireweed grew really well, but the large size meant it caught a lot of the current and was easily dislodged. The Dudresnay’s whorled weed Dudresnaya verticullosa was growing really well (see here) but broke off from the rocks and could not be replanted:

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I could not attach the fine red seaweed (see last post) either and did not want to have it floating around so I have removed it. My nice red seaweed streaming from the pump outlet, most probably Devil’s tongue weed Grateloupia turutu (as the name indicates, another invader from the Pacific), broke of. A crap picture of both weeds:

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I changed the white gravel with finer, beige Maerl gravel (Cornwall’s equivalent of coral sand, see previous post) here placed in a bowl for contrast:

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I released my Shanny as well as the largest of the two Rock gobies. The former attacked to many of the snails (it was getting a bit of a mollusc graveyard) and the latter was just too voracious in general. The final straw was seeing it swimming around with half a Worm pipefish sticking out of its mouth (I still have a bunch of those). The Shore rockling did not survive, but I caught a glimpse of the Shore clingfish when I removed some of the rocks from the aquarium. The juvenile albino Edible crab (if that’s what it is) and the European sting winkle Ocenebra erinaceus I recently caught both still do well, as is a juvenile Shore crab Carcinus maenas:

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The Netted dog whelk Hinia reticulata is not one of the most impressive looking snails, but they do very well in the aquarium, burrowing and moving around:

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I am not sure whether replacing one of the actinic lamps with the daylight lamp was such a great idea, the tank looks too yellowish now, especially with the Maerl sand…However, I will stick with it and see whether it helps future attempts to successfully keep Bushy rainbow wrack Cystoseira tamariscifolia (i.e. to retain it’s iridescence). If not, I’ll go back to the original lighting. I will not do too much with the aquarium in the near future as I want to get rid of the algae first. There are not many critters in the tank, which should help (I have only introduced a nice big Snakelocks anemone Anemonia viridis recently). I will do some more water changes and order a new pump. Only then will I slowly start experimenting with seaweeds again.

I am still unsure about the chiller, but with the weather getting warmer it might be more than just a luxury to have one. Apart from the price, it standing on the floor next to the aquarium with tubes sticking out is what I don’t like about the idea though. It will also not be silent, but perhaps I could get away with disabling the noisy hood fans, resulting in an overall quieter aquarium. The stripped-down tank (note that the red encrusting algae/seaweeds at the top of the tank have died (turned white) as they were exposed for a couple of hours when changing water):

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