Species details: Crangon crangon

I always manage to catch at least a few brown shrimp whenever I go shrimping, irrespective of location, time, tide, or time of year. They do alright in the aquarium, although they do not seem to like temperatures much above the 20 degrees Celsius. They prefer a sandy substrate and spend most of their time buried, with only their eyes protruding, but are easily tempted into showing themselves with frozen or flake food, and also come out at night.
They do not do well in the presence of larger fish, and also have a habit of bumbling head-first into waiting anemones. I guess they do not encounter many anemones in their natural habitat, and they do not seem to be able to avoid them as easily as a prawn can, for example. Although they are a bit drab, they are actually quite entertaining to watch and exhibit a range of interesting behaviours. They are interesting inhabitants and do well, provided they are kept separate from their natural predators.

Species details: Carcinus maenas

Shore crabs are easy to catch and ubiquitous, and they adapt extremely well to aquarium life, being tolerant of high temperatures, fluctuating salinity, and poor water conditions.   I still found that adding them to your tank is a very, very bad idea, as they are highly aggressive and make short work of their tankmates, including fish. Even small crabs grow rapidly, and they can be very difficult to remove, especially if the tank contains a lot of rock. They also spend most of their time hidden away out of sight, so the only sign of their presence is the dwindling number of other livestock. Luckily they are easily lured into traps. I would not recommend this species, unless kept on a tank of its own.

Equipment: Skimmer

Although not hugely powerful, the skimmer makes a big difference to water quality, especially when there is a mass sporulation of algae, which can turn the water a bit turbid. It's a good little skimmer that's unobtrusive within the tank, and produces about 50ml/day of concentrated skimmate if running smoothly. The only complaint I have is that the inlet hole is a bit small and regularly clogs with algae, which basically stops skimming. On the other end, the outlet also becomes clogged with algae, in which case it over-skims. I guess most marine skimmers are not designed to cope with large amounts of vegetation as most will be run in reef systems. If I were to set up a new system, I would probably choose a model with larger inlets and outlets, or attach some form of strainer to keep out algae.

Equipment: Lighting

The tank is set up to simulate the environment of the lower shore of the English Channel, so good growth of macroalgae is an important issue. I have tried different combinations of different tubes, and found that this one gives me the best growth while also giving attractive lighting. I used to have two Power-GLOs, but I found the light to be too red, and the colours of the animals and plants weren't as luminous as they are now. Plant growth is very good with the current combination.

Equipment: Cooler

There are very few species that can be kept successfully for any stretch of time without a cooler. I can't think of any fish, only prawns and beadlet anemones, as well as common shore crabs.
I have got a 300W model, but in retrospect I would probably go for a more powerful model. My cooler is a bit noisy, I don't know if this is a feature of the model in particular, or just my particular one. It was advertised as being quieter than a domestic refrigerator, but sound more like a washing machine. It does the job though, and takes about an hour to cool the water by one degree.
The back and sides of the tank itself are insulated with aluminised foam, and the tubing to and from the chiller and external filter are covered with plumber's pipe insulation.

Equipment: Pumps

I consider good flow to be vital for the maintenance of the tank. I initially had weaker pumps, but only when I switched to Koralia Hydor 4 did blue-green algae stop being a problem. I also get the best flow of macroalgae in the regions of highest flow, probably because the area is kept clear of more loosely attached nuisance algae. My two pumps are at opposite ends of the tank and run constantly, but presumably the results would be even better if they were pulsed to increase turbulent flow. I might even upgrade at least one of them to an even more powerful pump.
Maintenance is a constant chore with these pumps as the inlet slats quickly become clogged with fragments of red algae. I have high levels of primary production in my tank, and the removal of algae is one of the main mechanisms of phosphate and nitrogenous waste removal. I only do a partial (1/4) water change every six months (!), and the phosphate and nitrate levels nevertheless remain below the detection limit of the commercial tests. I used to change the water much more regularly, but I found that this only upset the stability of the system. My tank is not comparable to a tropical reef system because of the lush growth of algae, and frequent removal of algal biomass is very efficient in removing pollutants.

Species details: Spinachia spinachia

I originally had three, all from Falmouth (Cornwall), but only one grasped the concept of frozen food. As the other two only accepted live food even after a month, they got to go back to sea. I like this species for its uniquely rigid posture, a bit like a horizontal seahorse, but feeding is really a problem. Even the one that accepts frozen food needs many feeds a day, presumably because the body is too thin to hold a lot of food in the stomach. Apart from that, this peaceful species seems hardy as long as temperatures are kept down.