Native marine aquaria are pretty scarce. Little information exists on how to be successful in maintaining healthy coldwater marine systems in domestic aquaria.

Hopefully this record of my failures, triumphs and ideas will assist others interested in keeping some of our fascinating, beautiful and often little known sea denizens in aquariums.

Sunday, 5 September 2010

The Importance of Snails

Forgive the dramatic title but I'm increasingly convinced that grazing by herbivorous snails is an essential mechanism in the promotion of coralline algaes over the lower green algaes like hair algae and Enteromorpha.

Enteromorpha quickly grows over all surfaces and coralline algaes are unable to compete. A week ago I boosted the number of herbivorous periwinkles and topshells in my tank by about 400%. Adding another 60 or 70. I had noted that in areas of strong coralline algal growth, especially in Kimmeridge Bay the number of snails per square metre was very high, approx 40 - 50.

In a week almost all surfaces previously colonised by Enteromorpha have been grazed bare and in its place new corroline algae, both branching and encrusting has flourished. Furthermore new wrack growth has been noted on previous areas that had appeared devoid of anything but hair algae.

It would be interesting to be able to create a snail-proof 'cage' in a Kimmeridge rockpool and see if Enteromorpha takes over when the heavy grazing is stopped from occuring.

In the British reef aquaria, therefore, snails can be used to naturally create the conditions for coralline algae to flourish. As an added bonus I never need to clean the glass! Interestingly coralline algae growth seems restricted to rocks, shells etc. unlike in tropical tanks where encrusting growths quickly cover pumps and glass. perhaps British winkles and topshells are also able to feed on coralline algae on very smooth surfaces? The commonly used Turbo snails used in tropical aquaria may simply not feed on coralline algaes?

I am convinced that its not enough simply to mimic sea temperature, natural light levels, salinity and chemistry to promote corraline algae. Grazing appears to be an important factor. The conversion of green algae to soluble excreted snail waste for the skimmer is also an excellent nitrate and phosphate exporter whilst releasing minerals back into the water for use by higher and more desirable algaes.

Saturday, 4 September 2010

Sea Squirts

I have just noticed a small colony of about a dozen or so sea-squirts - probably Ciona - growing on a small chalk rock. As these creatures grow from a free-swimming larvae it appears that recent fresh sea-water added to the tank had some larvae from this species which has subsequently started to grow.

Its odd though, that they all decided to grow on the same rock. This rock has been in the tank about 6 months and originally had a single small mussel on it which was prey to a dog whelk. It was found above the shoreline after a storm and had probably been in the air for about a day so its highly unlikely that a sea squirt could have stayed alive on it. According to most information available on sea squirts they dont survive being removed from the water for very long at all.

Perhaps there is some kind of mechanism that enables larvae to colonise a place together via a chemical signal? Bearing in mind that I employ strong circulation, any signal would have to be 'sticky'. However, the chosen rock is in an area of fairly calm water. Maybe thats all thats required - a suitable area will be colonised and thats it.

Spider Crabs

I recently caught 2 of these small unidentified spider crabs hiding in thick corraline algae on the side of a rockpool. Possibly from the subfamily Pisinae, formal identification would involve stripping the creature of its camauflage, which seems unneccesarily stressful. I'll wait for it to moult. The carapace is about 25 - 30mm at present, the nostrum appears to be quite long and pointed. Pincers are small and delicate and the legs are quite short.

The camauflage is exceptionally effective. The crab carefully selects small, often living pieces of alkgae, passing them to its mouth where it appears to mumble something upon it which allows it to then stick it to a part of its body. All parts are covered in a garden of living algae except for the pincers and underbelly. The crab seems to spend a considerable amount of time in maintaining this garden. Its practically invisible!

probing in the sand with its pincers - presumably for worms?

investigating a newly introduced mussel

hanging upside down on a 'woody' algal branch feeding on algae. a few minutes later it found a tiny topshell which it delicately extracted form its shell and ate.

apart from the pincers the creature is impossible to differentiate from its surroundings

Friday, 3 September 2010

The 'Natural' Approach

Although a fish tank is by its very definition an artificial enviroment we can do a lot to make it as natural as possible. I dont mean just making it pretty with plants and nice rocks - I am talking about the conditions for biological process.

Many reefkeepers invest in hugle expensive mechanical filters, I've done so myself, and buy all sorts of stuff to put in them. Bio-Balls, filter pads, charcoal, phosphate removers etc. All have a place in fishkeeping - but are they really necessary? Are they even desirable?

I believe that simple, low-tech solutions can be found to almost all of the problems reefkeepers are likely to encounter by following as natural a route as possible. Using 'live' substrates and aquascaping. Fresh seawater for water changes. Encouraging macro-algal growth. Employing a clean-up crew. All these will greatly enhance the effectiveness of the nitrate cycle and improve water quality far better than any mechanical filter can hope to acheive over any period of time.

In addition, it cannot be underestimated how much easier the maintenance of a 'natural' aquarium is. Filters clog up rapidly and if the cleaning regime is neglected the filter itself will act as a nitrate bank, it may even 'go bad' and dump toxic sulpher dioxide into the tank causing a wipeout. The more stuff you have plugged into your tank - the more work is required to keep it functioning and the more disastrous it is when they fail!

Thursday, 2 September 2010

Even more pics

A juvenile grey mullet with a corkwing wrasse

A few close-ups of various small areas of the tank showing numerous plant species including corraline algaes.

A few more pictures

Common prawn in its favourite cave
New horn wrack growing on old rock

Juvenile corkwing wrasse

strong growth on Irish Moss

The tank

Wednesday, 1 September 2010

The Clean Up Crew

Converting dead vegetable and animal matter, uneaten food, decaying plants, casualties etc to a soluble form is greatly enhanced by the 'clean up crew'. By eating nuisance algaes, uneaten food etc and passing out excreted waste that is swiftly blasted into a soluble form by the strong circulation, the skimmer is able to swiftly remove unwanted organic matter from the tank.

Snails swiftly convert hair algae to faeces which the skimmer removes. Cushion stars, brittle stars, hermit crabs and netted dog whelks all play an invaluable part in converting detritus, dead matter and insoluble faeces to soluble organic waste for the skimmer to easily remove.

To maintain a healthy natural reef aquarium a clean up crew is indispensible.

Unfortunately many kinds of crab - but especially shore crabs and swimming crabs - as well as Shannies love eating snails and hermit crabs. Therefore I've tried to exclude these creatures from nmy aquarium - although they are tenacious hitchers on live rock!