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.

Tuesday, 31 August 2010

Skimming - Part 2

Its probably worth elaborating a little on why skimmers can be such an essential part of any reef set up.

There is no more effective way of saturating the aquarium water with dissolved gases. Without a skimmmer the only way gases are going to get into the tank to be used by the inhabitants is via the surface. Aquariums have a tiny surface are compared to any natural habitat. Airstones are OK for a short while but soon a scum will be noticed forming where the bubbles reach the surface. Unless this is removed it will inevitably add to the organic load of the habitat. No airstone is anywhere near as effective at maximising the amount of gas to be dissolved into the water as a counter-current skimmer.

Unless a mature, balanced and healthy deep sand bed within a refugium is being used it is almost impossible to maintain a healthy reef tank without a skimmer unless almost constant water changes are carried out. Even then the jury is still undecided - there have been a number of dismal failures recorded with deep sand bed techniques.

There is no more effective way of removing soluble organic waste. The key word here is remove. All that most filters will do is carry out some part of the nitrogen cycle - almost always raising the nitrate level. Anaerobic nitrate removers are tricky to maintain and have never really caught on.
Skimmers, if operated correctly, produce surprising amounts of brown sludge from otherwise pristine looking aquariums. This foul muck would otherwise be left in the tank for the overloaded filter to deal with.

Monday, 30 August 2010

The Nitrogen Cycle

The nitrogen cycle is probably the single most important biological process in the aquarium. Whatever food is introduced into the tank will eventually undergo biological decay via a process called the nitrogen cycle.

Waste food, faeces, and dead organisms rapidly undergo a biological breakdown producing ammonia which is extremely toxic to marine life. Luckily it is eagerly eaten by bacteria producing Nitrite which whilst still toxic is markedly less so. Further bacteria then turn the nitrite to nitrate which is a far less toxic and most aquariums contain fairly high levels of nitrate.

The cycle of food - ammonia - nitrite - nitrate is absolutely fundamental to maintaining a healthy aquarium and commonly takes 3 to 4 weeks to become established as colonies of bacteria grow to meet the demand.

A number of filters have long been used to facilitate this cycle. The conditions required for bacterial growth are food, oxygen and water movement. Undergravel filters were the 1st breakthrough. A plate was fitted beneath the substrate, through 100s of tiny holes water was pulled downwards through the substrate to the plate where vertical outlets came up to powerhead pumps. This created a rapid flow of oxygen rich water through the substrate which allowed for a massive surface area to be colonised by areobic nitrogen reducing bacteria. However, the substrate rapidly became clogged with detritus and within a year or so would become a huge nitrate bank, leaching nitrate into the water.

The next major advance was the wet/dry filter. Usually a vertical column outside of the tank filled with a suitable material that provided the largest possible surface area with a trickle bar above allowing just enough water flow to keep the substrate wet without total immersion. these proved enormously efficient and allowed a much greater range of creature to be kept. Nitrate levels would, however, still rise. Large and regular water changes were required to export nitrate.

Various other methods have been employed to check nitrate levels to allow the keeping of more sensitive creatures, especially hard corals which cannot tolerate nitrate levels above 5ppm. Algal scrubbers, a corrugated tray with a flow of water beneath a permanent light allowed the growth of hair algae which could then be harvested. All plants use nitrate and algal scrubbers are effective at lowering nitrate levels but also take up large quantities of minerals which then have to be replaced with supplements.

More recently advances have been made in allowing anaerobic conditions to exist which creates the necessary conditions for another bacteria to eat nitrate producing nitrogen gas which then harmlessly bubbles through the substrate to the surface.

In tropical tanks this was acheived by using large quantities of 'live rock'. This is rock formed by dead coral. Extremely porous it allows a slow transfer of water through its centre and has a vast surface area relative to its size. Aerobic bacteria live within the 1st few milimetres and brakdown soluble waste to nitrate which deeper in the rock where no oxygen is present is further broken down to harmless nitrogen. A similar process can be created using a deep live sand bed.

I try to create these conditions in my native marine tank by using live sand taken at low tide with plenty of the underlying black sandy mud, rich in micro-organisms. Also porous rocks such as chalk from below the tideline will already have colonies of all the necessary bacteria to carry out the nitrogen cycle.

Seeding a new aquarium with live materials such as rock, sand and seawater eliminates the wait for colonies to develope before introducing livestock.

To effectively encourage nitrate eating anareobic bacteria to thrive a deep sand bed is required. Remove any filters that are designed to creatre nitrate so that the process can be carried out in the sand and rocks. Encourage the growth of macroalgae. Use skimmers to remove as much soluble waste as possible initially.

Using this system I have been able to keep nitrate levels below 5ppm for over a year with no water changes.

The next step is to reach the stage where the skimmer can be turned off which will allow the growth of plankton allowing the keeping of bivalves, soft and hard corals and sea pens etc. I intend to expand my system as follows:

Build a much larger display tank - 6' x 2'6" wide and 3' deep with halides above. The tank will be drilled allowing a 2" pipe to fall to my current 3' x 2' x 2' tank below , which will become my sump tank. The sump will have an 8" live sand bed covered in porous rock such as tufa with permanent lights over for plant growth. A return pump will then go back to the new display tank.
The display tank will have a 10" sand bed and landscaped in live rock. All water will be taken directly from the sea. Circulation will be carried out by 4 no. 5800 l/h pumps. only 1000 l/h will pass through the sump allowing plankton to develope which will trickle up to the display tank feeding the livestock.
It is hoped that skimming will not be necessary. All of the nitrogen cycle will take place slowly and naturally with excess nitrate being taken up by the strong algal growth in the sump which can be harvested and disposed of as and when necessary.

I had a similar system in my tropical marine reef tank for many years, mangroves were grown in one of my 3 sumps which are excellent nitrate exporters. No British equivalent to the mangove exists - but perhaps an eelgrass bed could be maintained?

Sunday, 29 August 2010

Collecting Specimens

Probably one of the best things about keeping native marines is going rockpooling with the kids and catching all sorts of exciting fauna to take home and study. We use a couple of 15 litre buckets and a variety of nets,

I only take home the creatures that I know will be suitable for a community reef tank. Sea scorpions are fascinating, easy to catch, rather beautiful in their own way but will swiftly decimate the rest of the inhabitants. Shanny are great pets, intelligent, lively, comical and very easy to keep - but they will make short work of interesting and useful creatures like shrimps and hermit crabs.

A couple of years ago I caught a shoal of 8 mullet about an inch long and also at the same time in the same shoal a tiny bass. Within a year the bass ahd grown to 6" and eaten everything else in the tank, furthermore this voracious predator generated such an amount of waste that water quality began to deteriorate so I released him back to the sea. Although the bass was a very interesting creature and looked great shining brightly as he prowled around looking for something else to eat he simply was not suitable for the tank I wanted to create.

Pipefish are fascinating subjects. But they should not be housed with snakelock anemones - they fall prey far too easily. Furthermore they are difficult to feed although mysis shrimp and rotifers can tempt them to feed they must be closely monitored and released if they dont appear to be eating.

The collecting and subsequent transport back to the tank is the most hazardous part of the whole process. Water in a bucket on a sunny day rapidly heats up, oxygen levels fall and livestock can quickly succomb. Shanny and snails are largely bulletproof - anything found in small rockpools high up on the shore will be used to massive fluctuations in temperature and salinity, but even so, its only fair to do as much as possible to reduce any stress to the animals.

Its a good idea to use a battery powered cooler in the car to transport the collection with a battery powered airstone to oxygenate the water. anything caught below the shoreline will need extra care during transport to minimise mortality.

In practice I have found mortality levels to be very low. I live near the sea and rarely take longer than an hour to get the animals into the aquarium. For me the greatest risk is immediately upon release into the tank. Frightened small fish have a habit of blundering straight into the anemones! A holding tank to allow the animals to stabilise at the cooler temperatures of the tank is a good idea. Turning the main pumps off at the time of release helps new arrivals to find a hiding place before being blasted into the waiting arms of a snakelocks.


Undesirable algaes are all too easy to cultivate and without large numbers of snails to graze it away my tank would swiftly be overgrown with hair and slime algae. The problem is that as fresh macro-algae dies it dumps it minerals and nutrients into the water which is exactly what nuisance algae needs to thrive. The skimmer can only remove the organic waste and then only as its dissolves to a waterborne form.

Desirable algaes are very tricky though. To date I've always struggled to keep them alive for more than 10 days or so. I'd collect a great rock with a nice bit of Horn Wrack on it, withion 3 or 4 days it would start to fray and darken, the skimmer would go into overdrive and within 10 days it would all be gone!

So - I upped the lighting. But the water go too warm so I got a chiller. It also occurred to me that salinity might be an issue so I've adjusted that to match local conditions. Hopefully I've satisfied all the criteria and yesterday added a few more rocks with macroalgae on them, including a small horn wrack. I'll post the results.

31.08.10 - Just spotted 3 healthy, small horn wracks growing back on previously bare rocks. Looks like the combination of cool water, bright light and correct salinity have cracked it!


I fell into the trap of getting salinity wrong. At 16C a salinity of 1.026 is required. The average salinity around Britain is 1.025 but the western coast is slightly saltier.
I collected my sea water from the ferry slipway at Sandbanks in Poole on an incoming tide, even so the salinity was only 1.023 and I had to boost it slightly with a saltwater mix.


Desirable algae - as opposed to unwanted and horrible hair and slime algae is very difficult to keep. To date I've not been able to get it right although I hope I've satisfied the criteria required with my latest efforts.

Previously whenever I've had a great rock with a nice clump of wrack, after a few days its started to fray and darken. Within 10 days its gone and the skimmer has been working overtime. Initially I thought this was a lighting issue so boosted the lights as much as possible. Then I thought it was a temperature issue so brought a chiller. Then I thought it was a salinity issue (see seperate post on salinity). I believe that now I've got all the paremeters right and yesterday added a small amount of horn wrack. Hopefully I've finally cracked it!


The tank is lightly stocked as far as fish goes. To maintain water purity I plan on feeding as sparingly as possible. A number of undesirable have crept in unnoticed on rocks, but as I regularly release stock and replace with something different this isnt a huge issue.

Below is a list of the livestock

2 no. Corkwing Wrasse about 1" long
2 no. thick lipped grey mullet 3/4" long
1 no. shanny 1/2" long (undesirable hitcher on rock)
at least 4 no. crab- probably shore crab about 3-5mm (undesirable hitcher)
10 no. common hermut crab - shell size of 5mm - 12mm
85 various snails - including flat periwinkle, edible periwinkle, banded periwinkle, toothed winkle, flat topshell, grey topshell and 2 no. netted dog-whelk
12 no. beadlet anemone
20 no. snakelocks anemone
4 no. warty anemone
2 no. unidentified spider crab - heavily covered in seaweed camouflage
6 no. common prawn
5 no. mussel
4 no. blue cushion stars 2mm - 10mm
~6 no. brittle stars approx 1mm body size - really tiny

This list is not exhaustive, every day almost I see something new that hitherto had remained hidden on a rck somewhere.

Good fishes include the mullet which doesnt harm anything and grazes on algae
Shanny are voracious, intelligent and omnivorous, the suck hermit crabs out of their shells and rapidly demolish barnacles.
Bass grow very rapidly and eat everything
Tompot blennies are even more voracious than Shannies - they will even eat anemones!
Wrasse are good grazers but take chunks out of anything - they nip at snails and barnacles and dont seem to like company much - I have 2, one will have to be released soon as its getting bullied by the slightly larger one
hermit crabs are excellent - part of the cleanup crew
snails are essential for the grazing of algae, under my lighting conditions hair algae growth is very strong, large numbers of snails - roughly 4x natural density is currently used to bring growth under control - then most will be released back again.
Shore crabs are almost impossible to keep out but have to be trapped and removed as soon as they grow over 30mm or so when they can become a serious predator.
Netted dog-whelk are a great scavenger and rapidly eat leftover foods
Prawns are another essential part of the clean-up crew
cushion and brittle stars are great scavangers of organic detritus that accumulates in hard to get at corners

I feed all the inhabitants on frozen brine shrimp and frozen rotifer. Occasionally I also add a single frozen whitebait or 2. Feeding is light - about every 48 - 72 hours a single cube of either.

Setting Up

The substrate of my tank is a wheelbarrow full of sand from Studland Beach taken at low tide near the water. An inch or 2 down and the golden sand is black with anaerobic mud - this is the good stuff! Studland sand is a fine golden sand which is possibly a little too light for the circulation I employ - its too easily stirred up and without the canister filter would have kept the water murkey. After several months its pretty stable and has a thriving population of worms and bacteria.

The nitrogen cycle takes place within this mud and unlike canister biological filters, wet/dry filters and undergravel filters whcih gradually raise the nitrate levels to high levels which are then almost impossible to lower a natural anaerobic mud bed breaks nitrate down to nitrogen gas which harmlessly bubbles to the surface. My sand bed is only 2 - 3" deep, ideally I'd have a deeper tank and a bed of 6 - 10".

Landscaping in the tank consists of a number of different rocks - all 'live', ie taken from below water and encrusted with life. I have some great chalk rock with beadlet and snakelock anemones, barnacles and bladder wrack. Chalk is an excellent rock for aquariums, its a great buffer rock for maintaining pH and hardness. As its porous its also excellent for natural filtration allowing a slow and steady conversion of organic waste to nitrogen in its anaerobic core.
Additionally I have flint nodules and Kimmeridge Shale. The Shale is thickly encrusted with Corallina officinalis and other pink calcareous algaes.

The foreground is largely sand, the back and sides are piled up with rock.


To be honest I dont really use the canister filter as any kind of biological filter. I have a couple of bags of charcoal in there and the rest of the filter is full of foam pads for the removal of suspended particulates. If I had a drilled tank with a sump I wouldnt need a canister filter at all. I dont want the nitrate cycle to be speeded up in a biological filter...more on that later.


Protein skimming is a simple, yet extremely effective way to greatly improve water quality in saltwater aquaria. The principle is that air bubbles attract protein molecules and form a scum. This scum is collected via a cup at the top of a vertical tube for disposal. By removing proteins (uneaten food, excreta, dead material etc) before the nitrogen cycle has begun greatly reduces the speed at which nitrates build up in the tank. In addition skimmers are extremely effective at oxygenating the water allowing for increased stocking levels.

I collect a glass of disgusting brown paste every 2 or 3 days which would otherwise be fouling the water.

The downside of skimmers is that they are also excellent at removing plankton from the aquarium, when feeding soft corals, bivalves and other plankton feeders its a good idea to turn off the skimmer for a couple of hours or so.


I am a strong believer in ciculation as an essential element in marine aquaria. In the wild sea creatures are subject to constant chaotic flow and with all the elements added together I have a water movement of over 16000 litres an hour!

I believe strong circulation is essential to maintaining good water quality, strong currents greatly assist in the breaking down of organic waste for removal by the skimmer. Anemones, mussels, clams and barnacles need good water flow to feed successfully. I have noticed that nitrate levels in all marine aquaria stay lower with better circulation.


I brought a Cornelius beer chiller on Ebay for £50, I've no idea which model it is although the seller advised that it was purchased to chill 2 kegs of homebrew at a time. The thermostat goes up to a maximum chill of 7. It has 2 lines in and out.

With no chilling at all the temperature in the tank under the lights can rise as high as 32C!

The chiller took 3 days to take the temperature down to 16C and now sits on a setting of 2 to maintain this temperature. The air temperature has been around 20C and it appears that the chiller stat will need careful monitoring to keep the tank at 16C as the air temp changes with the seasons. However, 50 gallons of water takes a while to heat up or cool down so monitoring does not need to be constant.

The chiller itself generates a lot of heat, I propose to relocate the chiller to the utility room adjacent to my office where I keep the tank.

Plumbing in the chiller
The chiller came with 8mm stainless steel inlets and outlets, this is an unusual size to get fittings for so I had to find a way to adapt. B&Q sell 8mm clear polythene hose for about 50p/metre, by softening the end in boiling water its possible to force the hose over the steel then a clamp can be used to hold it securely although it probably will not come off anyway. The 2 outlets simply have a length of this hose extending directly into the tank. At the inlet end its rather more complicated, the pump I used has a 20mm nozzle, to this I attached a short length of 20mm hose, once again I softened the hose in boiling water to force it over the nozzle, outside the tank I then inserted a short length of 15mm John Guest Speedfit pipe with the appropiate plastic insert to stiffen it and used a hoseclamp to tighten. Then I used a 15mm tee with 10mm reducers to connect to the 2 8mm plastic inlet hoses from the chiller. Once again I softened the 8mm hose and forced in a 10mm speedfit insert to stiffen the tube and this formed a tight seal when pushed into the 10mm reducer.
Its important to use only plastic pipe and fittings, ensure the inserts are plastic too. Metals will quickly corrode and poison the inhabitants - anemones are particularly susceptible to metallic poisoning.


The few references on-line that offer any information at all on the keeping of British marine life all agree that lighting is rather unimportant and our dull waters are simply not used to light - a single tube is usually deemed sufficient.

Its my own view that most of the creatures you are likely to keep will be found in rockpools. They will be used to very high levels of light and its probable that even tropical quality halides will not be able to match the levels that may be required for the successful keeping of many algaes found near the shore.
Therefore I use as many lights as I can fit on the lid and boost them with reflectors to maximise the amount of light. Ideally I'd use metal halides but I'm hoping that I can keep algaes successfully under flourescents - time will tell.
This much light under a tight lid generates a lot of heat, I've not been able to find anything anywhere near as good as a chiller for keeping the temperature at the correct level.

I run the lights on a 12 hour cycle with a simple mechanical plug timer, make sure its rated to carry enough current for the number of lights to be used.

Getting Started

I'll list my basic kit 1st and try to explain further on subsequent posts

Aquarium - 10mm glass tank 3' x 2' x 2' holding approx 50 gallons

Lighting - 4 no. 30" T8's (2 actinic and 2 marine white) and 2 no. 34" T5's (1 white and 1 actinic) in a purpose-built tight-fitting timber hinged lid with reflectors.

Chilling - Cornelius beer chiller with 2 outlets from Ebay (£50) with New-Jet 1700 pump pushing 1700 litres/hour through coils

Circulation - 2 no. Marea Propeller magnet mounted pumps at 5800 litres/hour each

Skimmer - Skimmer Beast 400P skimming 1100 litres/hour

Filtration - Eheim Professional 3e canister filter pushing 1500 litres/hour