World-Class Reefing: Mark Ratcliffe's 250-Gallon SPS Tank

Author: Richard Aspinall

A large reef tank is always a sight to behold, but one that is thriving with a variety of vibrant corals and fish is absolutely stunning. Our author went to visit Mark Ratcliffe’s impressive aquarium and explains exactly how he is so successful.

Reefs That Leave You Speechless

Mark Ratcliffe’s reef tank has been receiving a great deal of attention over here in the UK, winning Tank of the Month status on a leading web forum and appearing in a UK magazine. When I met Mark, he showed me his fishroom, offered me a seat on his comfortable-looking sofa, and disappeared to the kitchen to make coffee. When he returned five minutes later, I was still in the same spot, mouth agape and utterly transfixed at one of the finest systems I had ever seen.

Seeing Mark’s reef leaves you pretty much speechless. Not only are his corals and fish in perfect health and condition, his fishroom and technology are on the cutting edge of the hobby. Everything is superbly put together, and each piece of equipment contributes to water quality that is as good as anyone is likely to achieve.

The Tank

Mark’s 78 x 30 x 30-inch, 1,000-liter (250-gallon) system resides in an uncluttered viewing room with cleverly hidden and boxed-in piping and cabling running into a fishroom next door. The refugium, sump, and settlement tank bump the overall volume up to 1,650 liters (363 gallons), and as you sit and watch the reef, there is little hint of the technology at work on the other side of the wall.

Mark’s system has been running for around 18 months in its present configuration. It started out as a large but conventional system, with a sump downstairs connected to the tank via a conventional corner weir and two 50-mm drains. He progressed to adding a separate refugium and frag tank in a cupboard before moving to the two-room solution we see today. Before looking at the inhabitants of Mark’s system, let’s look at the technology that creates such stunning water quality.

A Dedicated Fishroom

A dedicated fishroom is the dream of many. In effect, Mark has two—his viewing room and a utility room that holds a huge amount of equipment. The latter is the envy of all who survey it. Water from the main system flows via gravity into a large settlement tank through a 200-micron filter sock. This tank is drilled at the bottom and allows Mark to easily dispose of waste water to the drains when he is carrying out a water change.

Above this tank is a reservoir for making fresh water, which is then allowed to flow via gravity straight into the settlement tank. Far easier than contending with old salt buckets and flexible siphons like many of us do! A pump in the settlement tank also feeds a chiller. Marks’ auto top-up unit uses a 25-liter (6-gallon) container in the settlement tank fed by a 600-liter (150-gallon) container in his garage, on the other side of the wall.

Water continues into the main sump, which receives all the returns from the frag tank and the Chaetomorpha-filled refugium (a 400-micron sock keeps macroalgae from entering the main sump). Mark additionally uses a twin-chamber protein skimmer fed by a 645-gallon-per-hour pump with a small ozonizer. The output from Mark’s calcium reactor also feeds into this tank.

Water is then returned to the main system, frag tank, and feed for the UV system and series of pods containing phosphate-absorbing media via two 7,500-lph (2,000-gph) pumps. Mark uses a “slow flow” method for reducing phosphate using a pod with a phosphate-reducing resin with a flow rate of around 5 lph (1.3 gph).


Mark uses T5 lighting with great success. He runs eight 80-watt tubes and two smaller 24-inch tubes to extend light to the corners of the tank. The rear tubes switch on at midday and are at full brightness by 1 p.m. The front tubes switch on at 12:30 p.m. and are at full brightness by 1:30 p.m. The four center tubes switch on at 3:15 p.m. and turn off at 9:15 p.m. The inner and outer pairs then start dimming down at 10 p.m., with the last pair being fully off at 10:40 p.m.

Mark has sunrise and moonlight illumination. Sunrise starts at 6:30 a.m. and is the only illumination until the main lights come on at midday. The moonlights are set to follow the lunar cycle for his home location. One pair of tubes (blues) is timed to switch on at 1:30 p.m., and these remain on until 10 p.m. The remaining four tubes then switch on at 3 p.m. and remain on until 9 p.m.

The refugium is lit with a 6 x 39-watt T5 unit, but only the four center tubes are wired to illuminate. The tubes are 6500K day lights. The lights are set to switch on at 10 p.m. and switch off at 1 p.m. the following day. Mark aims to replace the tubes in all the lights every nine months.


Circulation is provided by a mixture of pumps strategically placed to allow the flow to not only be random but give a good balance around the rock work and corals. Some are wirelessly controlled via a controller, and two are connected to a battery backup.

Left-Hand Side

The left-hand side features two pumps, one of which is mounted 6 inches down on the weir, pointing upward at a 45-degree angle to add surface movement. Another unit is set behind these to add flow along the rear of the tank. Some of these pumps are further controlled to allow for a feeding pause, where their output drops to 50 percent for a predetermined time interval (depending on the food being fed).

Right-Hand Side

One unit on the right-hand side is set as the master, predominantly to a “Reef Crest” setting at max speed. Using the controller, the speed can be set for all the pumps in steps between 0 and 255. The pump switches to the “Lagoon Random” setting at 10:30 p.m., and the speed drops to 200 at this time; it then reverts to “Reef Crest” at 8:30 a.m. the following day. For 15 minutes every day, starting at 7:30 p.m., the pump switches into “Nutrient Transport” mode to free any trapped detritus from feeding at 6 p.m. Should the main power supply fail, this pump is set to continue running on battery backup at 50 percent speed.


A left-hand pump is set as a synchronous slave running at max speed. During the night hours, from 10:30 p.m. to 8:30 a.m., it switches to anti-sync slave mode and runs at a speed of 170. This pump is also set to run from the battery in a power outage at 50 percent.

The pump at the right-hand rear is also set as a synchronous slave, but runs at a speed of 140. During the night hours, it continues as a synchronous slave and runs at a speed of 170. This one is able to sync with the master pump and also runs the “Nutrient Transport” mode.

The circulation in the frag tank is provided by a single pump running at a constant speed of 160. This, coupled with the flow from the return, is more than adequate.

Heating and Cooling

Two 400-watt heaters are employed to heat the tank. These are set independently to act as a master and a slave. The master is located in the skimmer section of the sump. If the temperature falls from a preset of 26°C (79°F), this heater kicks in. The slave is in the first chamber of the same sump. If the master can't keep up with the heat demand, this heater kicks in at 25.8°C (78°F).

Mark purchased a second-hand chiller, located outside in a small shed, in case the temperature in the south-facing sump room rises too much. This is fed with a 1320-gph pump from the settlement tank. The chiller is underrated for the water volume (it was borderline on the previous tank, he says) but does keep the temperature in check on really hot days. The chiller is set to come on at 26.8°C (80°F) to compensate for the time it takes to bring the tank temperature down to the nominal temperature.

Mark has two fan units over the main display, set to first activate if the temperature rises above 26.2°C (79°F) and ramp up to maximum speed if the temperature exceeds 26.4°C (79.5°F).


When the tank was first set up, Mark used the “Balling Light” method—a method of providing calcium, magnesium, carbonate hardness, and trace elements to an aquarium. As the demand for KH increased due to coral growth, he sought an alternative method for supplementation, this being a calcium reactor.

He additionally doses 10 ml of a trace element mixture on alternating days. No other additions are dosed, as he finds regular water changes maintain the tank's health and vitality. Mark uses a high-quality salt that is close to the parameters the tank now runs at.

Monitoring and Control

The system is predominantly controlled and monitored by an automated unit that Mark can access through the web. His Android phone has an app to allow remote monitoring, and the system is set to send an email with a status report of the main parameters (pH, temperature, redox, and the status of the level sensors) every two hours. If the email doesn't arrive, Mark says it is time to panic! The email notification is a good way to know that the system is okay and power to the house is still on.


The fish are fed four times per day. The first feed is a pinch or two of flake, usually around 7:30 a.m. Flake is then fed around midday. The evening meal is made up of a variety of frozen foods.

Mark buys frozen slabs of mysis shrimp, brine shrimp, and krill; adds equal quantities of each to a jug; fills it with RO water; lets it thaw out; and then mixes it all together and rinses it through a strainer with RO water. The mix is then divided up into ice cube trays and refrozen. A cube is fed every day at 6 p.m. along with a sheet of nori for the tangs.

The last feed of the day is at 9 p.m. This is either carnivore pellets mixed with the herbivore ones, or the complete-diet pellet.


Mark believes that general housekeeping is the basis of a successful reef tank. He says he may be construed as a bit obsessive and can often be found tinkering in the sump room or just observing the traits of the livestock. “Once you have established a routine and can learn the behavior patterns of the fish, then the rest falls into place naturally,” he says.

Water Changes

The volume of the water change is 170 liters (44 gallons), which equates to roughly 10 percent. The filter sock in the settlement tank is a 200-micron nylon type and is swapped out every three to four days. The water change/filter sock changes can be done by isolating the settlement tank so the system continues to run normally.


The skimmer cup is cleaned at monthly intervals due to the use of a self-cleaning head to keep the neck clean. The self-cleaning head cleans the neck every six hours. The skimmate that collects in the cup flows into a Davy Jones Locker (a collection bottle) that is emptied weekly. If the level of skimmate collected rises quickly for whatever reason, a sensor registers that the Locker is full and the controller will shut off the skimmer Venturi pump.

Chaeto is harvested every two weeks, and Mark pulls out a good carrier bagful each time. The glass on the main display is cleaned every two to three days. The internal pump assemblies are cleaned when they start to look like they need it, and when they have been done, there is a marked improvement in the flow they produce. The pump for the skimmer is cleaned every six months, along with the skimmer Venturi pump. Again, he doesn’t stick to a fixed routine with these; he believes in the mantra, “If it ain't broke, don't try to fix it.”


The only routine he has that is set in stone is taking a good look at the livestock every night, counting and checking the fish, checking the corals for any signs of damage, and giving the system a general once-over.


According to Mark, the one problem that springs to mind with this tank was coming home from work one day to find the living room carpet “squelchy.” Mark now uses a pre-filter in the PO4 pod setup, and it is tapped off the return line to the sump stack.


Mark is undeniably proud of his corals, especially their phenomenal growth rates. The system is predominately stocked with small-polyp stony (SPS) corals, most of which have been grown from frags and transferred from previous tanks.

Mark likes to keep his hands out of the tank as much as possible and lets nature take its course as it would in the wild. He has a small collection of large-polyp stony (LPS) corals, mainly to add color and movement to the front of the tank at sand level. As for soft corals, he has a few zoas and mushrooms that have found their own place on the rocks to settle.


Mark has a mixed selection of cleanup-crew inverts, virtually all employed for a specific role. People often ask him how he keeps the sand so clean. “I don't,” he replies. It’s the sand-sifting stars and the orange-lipped conch that do a fantastic job here.”

And Finally...

Before I cheekily ask him for a frag or two, I ask Mark about an upgrade. “Well, if, and I mean if it happens,” he says, “it’ll be an upgrade to the main tank, from here to here.” He paces out the dimensions of a system roughly twice the size, and I hope that “if” becomes “when.” Thank you, Mark, for your hospitality and the frag!