Techniques for Temperate Marine Aquaria 

At this point pumps and skimmers were installed.  I am currently using a Deltec MCE 600 "hang on" protein skimmer which is extremely effective.  My only gripe with this skimmer is that the rubber mounts for the ceramic impellor spindle seem to degrade over time causing annoying vibration.  Replacement rubber mounts are available for this quite cheaply however and by fitting these replacements the problem is resolved. A couple of Fluval 304  external filters provide mechanical and biological filtration and a Fluval internal filter is used to pump water through the beer cooler  (more on this later).  The flow rate through the internal Fluval is low due to the resistance of the beer cooler coils but is ideal for activated carbon filtration and Rowaphos phosphate removal compound.  The output from the internal filter is fed into the smaller tank.  A 27mm hole was drilled into the small tank about four centimetres below the top using a diamond encrusted core drill marketed for the purpose.  The level of this hole is about four centimetres higher than the water level in the large tank allowing water overflow from the small tank to run freely back to the large tank.  A 25mm bulkhead fitting was screwed into the hole and a a strainer was attached.  Overflow flow from the tank passes through the strainer and down the output pipe connected to the bulkhead and returns to the larger tank  This arrangement ensures the smaller tank water is cycled through the main tank system.

Before stocking,  the tank was allowed to work with filters and skimmers for a few days at room temperature.  The cooler was switched on and the temperature allowed to fall to 15° Centigrade.  At this point a few hardy fish were introduced together with a few topshells and periwinkles  The tanks was then left mature over the months and additional fish added.   

What sort of Seawater ?

My tanks use natural seawater.  There seems to be much discussion concerning the merits of real v. artificial seawater.  I live around five minutes from the coast and can deliver the water from sea to tank in twenty minutes before plankton perishes and water becomes toxic and oxygen deficient.  For those living further away from the sea, I would recommend artificial seawater, as there will be no risk from plankton dieback and subsequent pollution.  I have had no problem with disease or parasites using real seawater, however I am aware that artificial seawater is enriched with trace elements which are beneficial to many invertebrates and algae.   I do not collect water after heavy rain as salinity variations may occur.  Sources close to estuaries where fresh water run off are also unsuitable as salinity will be unpredictable here also.

I aim to change 25 % of the water every month.  This can be arduous as it involves carrying plastic jerry cans full of seawater up from the seashore at high tide.

Seawater is a solution of salts of nearly constant composition, dissolved in variable amounts of water. There are >70 elements dissolved in seawater but only 6 make up >99% of all the dissolved salts; all occur as ions - electrically charged atoms or groups of atoms:

Seawater also contains small amounts of dissolved gases (nitrogen, oxygen, carbon dioxide, hydrogen, and trace gases). Water at a given temperature and salinity is saturated with gas when the amount of gas entering the water equals the amount leaving during the same time. Surface seawater is normally saturated with atmospheric gases such as oxygen and nitrogen. The amount of gas that can dissolve in seawater is determined by the water’s temperature and salinity. Increasing the temperature or salinity reduces the amount of gas that can be dissolved.  

 Specific Gravity

Specific gravity is  commonly used by the aquarist as a measure of dissolved salts.  The range  should be between 1.015 and 1.025. The optimum figure most marine environments is between 1.020 and 1.022.  This would obviously not apply to a brackish tank . Most fish, and even invertebrates can adjust to a slightly higher or lower specific gravity, but as with all things marine, it should remain stable.  Hygrometers are available to measure this value however it should be remembered that these are designed to measure salinity of tropical tanks at 25 degrees

pH

A measure of the acidity or alkalinity of a solution. Neutral pH is 7.0; values below 7.0 are acidic, while values above 7.0 are alkaline. The scale is logarithmic -- so a pH of 5.0 is not twice as acidic as a pH of 6.0, it is 10 times as acidic.
The pH should be between 8.0 and 8.4.  The figure to aim here around 8.2 For stability of pH, a high carbonate hardness is desirable, around 100 to 125 mg/L (6 to 7°KH). Rapid variations in pH can stress fish and filter bacteria.

Ammonia, phosphates and nitrite/nitrates

Ideally these should be kept at undetectable levels in the aquarium, however  is usually impractical to keep nitrate at zero where fish are present. Most marine fish have a reasonable tolerance for nitrate and, with the exception of a few sensitive species, can tolerate 50ppm or above. On the other hand, many invertebrates, particularly corals and anemones, will start to suffer at nitrate concentrations as low as 10ppm. Protein skimming and regular water changes, as mentioned earlier,  limit nitrate build up, but where fish are present, nitrate will always accumulate.  I am planning to acquire a Sulphur Denitrator soon.  These device relies bacteria living on balls of Sulphur to remove nitrate from the water.  I plan to perform daily nitrate test from the point of introduction of this device to measure its efficacy.  I will post these results when complete.  A wide range of test kits are available to test for levels of chemical in seawater.

 COOLING

In general a temperate aquarium should be cooled.  There are some littoral[1] species that can be kept in room temperature tanks, however such systems will have lower permissible stocking densities to a more productive nitrogen cycle and greater oxygen load resulting from the higher temperature.    

There are a number of techniques available to cool the tank.  These include beer coolers, dedicated aquarium chillers and "home cooked" systems.  My first "home cooked" attempt involved removing the icebox and compressor from an old fridge and encasing the icebox plate in a polystyrene fish box, (very useful boxes, most aquarium shops will let you take them away).  A long length of aquarium tubing was coiled up inside the fish box and the whole assembly sealed and filled with water.  The compressor was started and the water in the fish box reservoir got cooler.  Seawater was duly passed through the coils and was colder coming out then going in. So far so good.  Things seemed to be working well however on examination some days later, it appeared that the contents of the reservoir had turned to ice.  In addition ice was spreading over the tubes leading from the icebox plate to the compressor.  The whole reservoir had become solid ice.  In addition, the ice constricted the polythene tubing and impeded the water flow.  The insulating properties of ice also reduced the thermal efficiency of the cooler.  At this point I managed to acquire a beer cooler from the back of a friend’s pub and this soon replaced the home made cooler.  I suspect that with some perseverance and maybe the use of some form of agitator (powerhead?) to stop ice forming, the gadget may have worked, at least up to a point. 

The pros and cons of different commercial coolers are described below.  

• Beer Coolers

Not the easiest devices to obtain, however try your friendly pub landlord,  Ebay or local free ad.  pages.  Expect to pay between £25-00 and £100-00 second hand on Ebay or free ad. pages depending on condition.  They do not last forever,  however they will cool the tank to around 8° - 10° below ambient temperature and are a useable alternative should funds not extend to a commercial aquarium chiller.  It is essential to keep them level in a well ventilated location and with the water reservoir correctly topped up. In addition, if the cooler has been used before, it is imperative that the cooling coils are flushed out before use. Beer coolers are not meant to be switched off frequently. Any thermostat control should be maintained either using the onboard thermostat not by switching the cooler of and on via an external thermostat.  Beer coolers are manufactured by IMI Cornelius and SI Industries amongst others.

ADVANTAGES	DISADVANTAGES
Cheap (Second Hand)	Short Lived (Compressors/Agitators wear out)
Reasonably effective	Thermostat can be unreliable
	Can be noisy

•  Proprietary Aquarium Chillers

  A wide range of these are now available of varying size and sophistication, A number of technologies are in use including standard compressor refrigeration, Peltier thermoelectric cooling and evaporative water column coolers.  

 Of these, the compressor types are more likely to have sufficient capacity, however always check manufacturers data to ensure the chiller will cool your tank to sufficiently.  The key figure is the temperature difference maintainable for a given tank water volume.  Treat this as an overestimate, i.e. allow some margin when specifying your cooler.  Most of the coolers on the market are primarily intended to keep tropical tanks from overheating rather than keeping temperate tanks at temperatures substantially below ambient. This needs to be taken into consideration before making your purchase.  Manufacturers or distributors can advise on suitability. 

ADVANTAGES	DISADVANTAGES
Effective	Expensive
Reliable Thermostats
Quiet

Other methods include electric fans in the hood, cold water fed through coils in the tank from the mains water supply, and home made lash ups similar to the one described above.  I would not really recommend any of these approaches. Fans evaporate the water, cold water from the household water supply is inefficient, not really environmentally friendly and definitely not good if you are on a water meter.  Home made lash-ups can work however these need to designed safely and carefully.  Best  option is to save up and buy a chiller.  Links to chiller sources are listed below. If funds will not stretch to this then go for a beer cooler. 

 I am currently using an IMI Cornelius Varitemp 250 twin coil cooler which seems to have a reliable thermostat, maintaining  a constant 15 degrees all year round.  The cooler draws about 400 Watts power.  It is important to keep the air vents clear of dust and debris and to maintain the water reservoir level to just level with the overflow.

I have included some links to chiller suppliers below.

Lighting

Light intensity around British Waters is much lower than tropical seas so temperate tanks have relatively simple lighting requirements.  A deep tank may benefit from the use of metal halide lighting however for all but the largest tanks, fluorescent tubes are adequate.   I currently use one 36 inch power glow and one 36 inch marine glow actinic fitted with reflectors to increase the light output.  The high UV spectrum output from the actinic benefits the symbiotic algae resident within snakelocks anemones.  

Feeding

Feeding methods depend very much on the types of livestock in the tank. I use a frozen mysis shrimps for pipefish and small wrasse, chopped muscle and defrosted cooked prawn for gobies, blennies, anemones, sea scorpions and gold fish flake for mullet.  Frozen saltwater multi-packs also provide a variety of food for most fish in the tank.  Pipefish are fussy feeders however I have found that snake pipefish will regularly take frozen mysis shrimps available from good aquatic retailers.  I also have a source of live mysis at the local docks which I am attempting to culture.  These are ideal for pipefish.  As with all aquaria, uneaten food should be removed.