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.

Saturday, 10 September 2011


Whilst the animnals we are likely to keep in a native marine reef are, by and large, very easy to feed. Some care does need to be taken.
Heres a brief list of the foods I have tried:
Frozen artemia (brineshrimp) is taken by just about everything, is easy to store and readily available for little cost. Perfect for 2 spot gobies, small mullet, prawns and beadlet anemones. Very small wrasse will probably ignore it if there is sufficient live food in the tank but as they grow larger they will supplement their diet happily with all manner of foods.
Frozen krill is less popular. Whilst most fish will take it. all too often they will spit it out again. Anemones are less fussy.
Frozen chopped cockles and mussels will be taken by mullet, but wrasse seem less than impressed.
Frozen whole mussel, in or out of the shell is enormously popular and provides a good meaty treat. The wrasse tear it apart and the smaller fish eagerly wait for scraps. Blennies will not hesitate to dive in for a bite.
Whole peeled prawns make a good mouthful for larger fish. My goldsinny is a voracious predator of prawns of all sizes and frozen peeled prawns are an easy substitute for live.
Mullet will graze on algae, especially hair algae.
So, they all feed eagerly on a range of foods. What care needs to be taken then? Well, ensuring that all fish get enough to eat is paramount. Feeding a whole mussel a minute before adding some frozen artemia ensures that the smaller fish all get something to eat while the larger ones are busy demolishing the mussel. I often add a peeled prawn or two with the artemia which keeps the goldsinny occupied. Variety is good. Try different foods, maybe at different times.
Live foods, if freshly caught are exxcellent. Occasionally I add a couple of hundred tiny prawns to the tank. The goldsinny goes crazy for them, the survivors of the initial frenzy are hunted in the weeks that follow, which keeps the goldsinny happily occupied. However, with a mass of rocks there are many hiding places and not all will get caught.
Its essential to observe the feeding closely, you need to be able to spot any problems early on to ensure the health of the animals. Species that are unable to compete at feeding time will need to be catered for or released. Adding live copepods, rotifers and phytoplankton may be necessary if small fish, fry or pipefish seem unable to browse effectively. If they seem to spend a lot of time searchinmg for food but rarely 'bite' then its likely that there is nothing to eat. There are a number of excellent online suppliers that sell the above foods. I use and can reccommend their product and service.
Large blennies are particularly good at depriving other animals of food. Tompot Blennies are aggressive and greedy feeders and other fish will struggle to compete, occupy them with a large meaty morsal then add something for the others whilst its occupied.
If you keep filter feeders they will need an adequate supply of plankton. If you dont have any you'll need to add it regularly. All this may seem rather obvious - but its easy to let things slide and think that chucking in a regular feed will do - it wont! Observe feeding closely, give them variety and interest, and keep an eye out for those struggling to compete. If you cannot feed an animal correctly - and theres no shame in admitting it - let it go.

Friday, 9 September 2011

'Sand Filter'

Although not really a filter in the conventional meaning of the word sand can play a vital role in water quality. This post in an extension and revision of previous posts that tentatively explained the importance that I gave to live sand as a filter in the aquarium. I feel I am closer to explaining why I feel sand is so useful. Hopefully this post will clarify.
Sandy shores are very different to rocky shores in basic ecology. There is no primary producer on a sandy shore except perhaps for seaonal diatom blooms on more stable surfaces or eelgrass beds. Food supplies are either plankton available for filter feeders such as cockles, or detritus. The fauna can be roughly split into three categories according to size.
  1. Macrofauna - Cockles, lugworms, crabs etc. Animals over 1mm.
  2. Meiofauna - animals smaller than 1mm larger than 0.05mm
  3. Microfauna - animals smaller than 0.05mm

Almost all of these animals are infaunal - they live within the sand. The vast majority are detritivores. Within the meiofauna alone there are 22 known Phyla! The amount of biomass is heavily dependant upon the particle size of the sand or mud. The finer the particle the greater the number of animals. Coarse grained sands are practical deserts, highly oxygenated but relatively devoid of life. Very fine sands are teeming with life even though only the top few centimetres are oxygenated and are often anaerobic below 80mm or so.

It follows that very fine sands, rich in meiofauna and microfauna can be effective at consuming uneaten food, fish and mollusc waste and decaying plant matter. This consumption appears to have a net reduction effect upon the nitrate levels as opposed to more conventional mechanical filtration heavily geared towards mineralisation (the conversion of organic compounds to inorganic).

My own aquarium, with a 120mm layer of very fine 'live' sand has, so far, maintained high water quality despite no cycling. heavy stocking and frequent feeding. Its my belief that the sand has played a vital role in maintaining ammonia, nitrite and nitrate at zero. Obviously a raft of other factors have also played important roles. Lighting to allow algal growth that takes up any nutrients and minerals, high flow within the display tank to keep things moving, heavy and constant skimming to remove soluble proteins, chilling to provide the correct temperature range for native organisms to thrive and planted live rocks encrusted with different animals and plants are all undoubtably important.

Monday, 5 September 2011

Detritus and Design

If you keep a planted aquarium you will generate detritus in the form of decaying plant matter. Native algaes have cycles of growth and subsequent die-off, almost as land born deciduous plants flourish and then retreat according to seasonal cycles.
This presents significant challenges to the temperate reefkeeper. Pump intakes in particular will be prone to clogging seriously impacting on the efficiency of such items as skimmers, powerheads, circulators and especially canister filters. To a certain extent we can design the system to avoid this clogging or alternatively to facilitate the effective removal of detritus. On my 1st native marine system I built a 3 stage sump specifically to allow removal of detritus. The 1st chamber held the skimmer intake, the 2nd chamber was a lit section with a plenum and 4" of live mud to effect nitrate reduction and the 3rd contained filter pads through which return water drained before being pumped back to the system. It was rather flawed, looked OK on paper, but in practice the high flow (2 x 6400 lph Ocean Runners) blasted the mud away instantly leaving only gravel, the filter pads were continually becoming clogged causing the pumps below to be starved of water and fish were often found flapping on the filter pads having been washed through the system.
I learnt a number of lessons by the failure of this design:
  1. Weirs need to have slots cut into them to strain out fish and larger items of detritus
  2. Keep the circulation to the display tank, its generally not necessary to have 13000 litres per hour running through the sump!
  3. Use power heads or circulators to move water in the display tank instead of relying on massive return flow.
  4. Use the 1st chamber of the sump to catch detritus and move the skimmer to the middle or end chamber, there will be far less risk of the intake becoming clogged.
  5. Use natural methods of detritus utilisation rather than employing mechanical methods that will require endless maintenance.

My current system employs a slotted weir, it has proved effective at keeping even the smallest fish in the display thank whilst allowing fine vegetable matter through. Larger algal break -offs are easily removed by hand when convenient.

I use a 10 gallon settlement tank as the 1st chamber with an 1 1/2" overflow to the main sump. A layer of sintered glass filter medium on the base of the settlement tank catches and holds fine detritus where colonisation of detritivores and bacteria is encouraged. It requires no maintenance for many months at a time - if ever.

The main sump, a 3' x 2' x 2' glass aquarium contains the chiller pump and return, the skimmer and the main circulating pump. The base of the sump has a 2" layer of shells collected from the beach. This traps any remaining sediment. I keep 6 oysters in the sump to filter the water further and additionally about 30 tiny prawns have found their way here and catch any food particles that end up here. I have no problems with any of the pumps clogging and the slower flow rate of 1300 lph allows even the finest sediment to settle. A population of amphipods and copepods has colonised the sump and is presumably feeding upon the sediment. Apart from adjusting the chiller temperature and emtying the skimmer no maintenance is required for many months at a time - if ever.

Therefore, rather than engaging in detritus removal I have concentrated on utilisation. Whilst larger items are removed from the weir once a week or so, all fine particles are encouraged to settle in the 2 parts of the sump assembly. Colonies of detritivores will undergo some recirculation back to the display tank and provide food for the inhabitants but generally the low flow rate allows a stable oxygen rich enviroment for copepods and amphipods to thrive. This is as close to nature as I am able to get. In the Ocean as plankton dies and sinks to the bottom vast numbers of microfauna exist to feed upon this 'marine snow', seeded by the live sand in the display tank a similar habitat in the sump should, in theory, develope and feed upon the detritus. Soluble protein waste generated by this process can be removed by the skimmer or undergo mineralisation on the surface area supplied by the sintered glass in chamber 1 or the shells in the main sump.

I could place a few inches of live sand in the sump as well, but the sand in the main tank is probably the main filter of waste in the system. I am interested in seeing what the colonisation of the sump consists of and have elected not to introduce microfauna deliberately. As mentioned previously I hope that sponges and squirts colonise the sump, lit only by a small blue LED no photosynthesis occurs in the sump and algae cannot grow there. It is hoped that the sump will mimic a deepwater enviroment and perhaps in time will prove every bit as interesting and colourful as the main tank.

So, the design of this, my 3rd native system, has been optmised to require very little maintenance indeed whilst providing habitats for a range of organisms from brightly lit rockpools and shallow shores and also a similar sort of habitat to that found below piers and jetties. I cannot mimic the great pressures found at depth, but am unlikely to ever find deepwater specimens anyway.

I have tried out other forms of detrituis removal. My 2nd system, featured in the 1st year or so of this blog had no sump and intakes for the skimmer and chiller were in the display tank. I had endless work in keeping the intakes free of vegetable matter, the chiller and skimmer frequently became so clogged they ceased to function and the use of flourescent lighting ensured that the keeping of plants was always a battle unless I kept a strict regime of expensive bulb changing. I tried using canister filters to remove waste but once again the intakes were frequently blocked. Without constant maintenance, uncoupling the filter and washing it out, going through the immensely frustrating cycle of trying to prime it again and make it work - only to have to clean it out again a few days later, the filter simply didnt work. I spent a huge amount of time and money trying to utilise canister filters and whilst they are probably great in unplanted fish only systems I feel that they are largely a cumbersome hassle in any kind of planted native reef. However, filled with activated carbon or Rowophos they do have a place in clearing water or removing specific pollutants on a short term basis. As a long term solution to water quality they have significant shortcomings however.

The amount of detritus generated can be minimised by good quality lighting allowing algal growth to be sustained. Little is known about the life cycles of many macroalgaes and many will undoubtably die off and regrow according to the seasons even under constant lighting and temperature. It is probably unavoidable that these cycles will occur no matter what, but good lighting and flow will almost certainly keep die-off to natural cycles rather than death by unsuitable habitat.

Whatever system a native reefkeeper employs it makes for a far more enjoyable hobby if the system design allows for minimum maintenance whilst allowing the maximum number of organisms to be kept in optimum conditions with the least chance of system failure due to mechanical problems. Dealing with detritus waste is critical to system health and your own enjoyment of your aquarium. Keeping it as natural and simple as possible will go a long way to keeping native reefs a pleasure, not an irksome chore.

Friday, 2 September 2011

Skimmers and Plankton

Despite my skimmer runnung 24/7 and producing very satisfying amounts of brown gunk it appears that plankton levels are unaffected. Common knowledge has it that skimmers remove plankton - it makes sense, it seems logical and therefore it must be true!
However, after reading a post in another blog where a temperate reefkeeper in Oregon, USA, employed a skimmer to remove plankton blooms from his tank with little or no success I began to wonder if plankton is somehow 'immune' from skimmer uptake. It may be worth examining skimmer gunk under a microscope to see if it contains live plankton. I have no doubt that soluble proteins are taken up by the skimmer, but if live plankton doesnt fall under that category, if plankton does not 'stick' to air bubbles and simply passes through the skimmer unharmed - this has major implications for all reefkeepers. It explains how coralline algal growth is able to colonise tropical systems despite heavy skimming, how squirts and those tiny little tubeworms are able to multiply and cover the backs of all those rocks and how undesirable algaes are able to spread.
If skimmers do not remove plankton then they have no apparent drawbacks whatsoever. At least in any system that requires plankton to feed filter feeders such as bivalve molluscs, non-photosynthetic corals and fan worms.
Perhaps native reef aquariums, benefitting from regular re-seeding of plankton from fresh seawater under optimum conditions may find that the keeping of soft corals, bivalve molluscs and other filter feeders may prove relatively easy. If native planktonic organisms are able to reproduce and thrive in our aquariums despite heavy skimming - as appears to be the case - it seems that it may well be worth considering using a plankton tow net and specifically looking to capture plankton to add to the aquarium in the hope that desirable plants and animals might therefore be propagated.
If plankton growth is a problem, green water etc, adding more filter feeders might prove the best way to control water clarity. A full - grown mussel filters 4 1/2 pints of water a day, adding a few dozen to a geen tank might prove far more effective than upgrading a skimmer.