Tanne Hoff's (Tanu) Reef Aquarium

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Introduction and Background:

It is a very big honor for me to have my tank being featured here as Tank of the Month. I've been keeping marine aquariums for about 14 years since I was 10 or 11 years old, starting with a very simple, small tank. It contained only some dead shells and rocks, one piece of live rock, a feather duster and a small sea star. As my experience and pocket money grew, I upgraded the tank a little with some small damsels and shrimps.

Now, I'm a diver and a biology teacher so I have access to an abundance of information which makes it easier for me to understand what's going on in my tank. I'm also one of the administrators of the Dutch Marine Aquarium Forum, www.zeewaterforum.net. I've contributed quite a few articles to the Dutch Marine Aquarium Magazine. It took quite some time, as well as some successes and failures before the tank became what it is now. My current tank was set up about two years ago.

The way I keep this tank IS successful, but I'm sure this isn't the only way or even the best way. It just works for me!


When designing this tank, I had several goals in mind. The first was to create an environment in which the fish would feel comfortable. The second was to keep lots of healthy small polyped stony (SPS) corals. I didn't want to keep just a tank full of rocks, but instead wanted to create plenty of "free space" in which the fish could swim about and the corals could grow. I also wanted the tank to be easy to maintain. Being a diver, I've observed in nature that most fish tend to swim OVER the corals instead of in front of them. I also didn't want the rockwork looking like the Great Wall of China.

Thus, I didn't use much rock. I bought the tank and stand second hand, and the tank had a very nice DIY foam backdrop which I wanted to keep. To make a long story a little shorter (I won't bother with discussing the accidents which required me to buy new front AND side glasses!), I filled the tank with RO water, added salt and the tank had begun operation.

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As I said before, I had some ideas to incorporate into the aquascape. I used different techniques to accomplish my goals. I used PVC tubing to connect some pieces of live rock. Tie-wraps and epoxy were also used to create an open, lightweight structure. I wanted the fish to be able to swim and hide, and I also wanted the rockwork to intermittently hide the fish from sight. I wanted to make sure the fish didn't HAVE to see each other all time, thus reducing aggression. I think I have used less than 100 pounds of live rock in my tank, a fraction of the amount commonly used.

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As mentioned earlier, the focus is on small polyped stony corals together with fish. But in my opinion it would be boring not to house other animals as well. Shrimp, snails, hermits, brittle stars, sea stars, different 'softies' and other animals also fit in with my view of a coral reef.


I have quite a few fish, and I strongly emphasize the fact that I added these slowly over about two years. Adding all these fish at once almost certainly would have lead to a tank crash! Many people ask what the trick is to having good water parameters even with such a high fish load. The trick is nutrient removal; protein skimming, water changing, vacuuming the sand bed and a huge amount of fast growing (i.e., nutrient absorbing) corals are all very important. I think many aquarists too often underestimate the impact of nutrient uptake by the corals. Here's a list of my fish:

  • 2 Yellow tangs, Zebrasoma flavescens - I've kept the first Yellow tang for about four years. When I set up this tank, I added another one, the smallest I could find. In the beginning they fought a little, but later they became accustomed to one another. Then, after about 18 months, some serious fighting occurred over a period of about two weeks. The fighting stopped after about a week or so. I haven't seen any fights since then. Although these fish are among the most common, they are also among the most beautiful!

  • Gem tang (below), Zebrasoma gemmatum - I've been very impressed with these fish from the first time I saw one pictured in a book but never saw one for sale. It took me literally years to obtain one! Even in Germany, nobody could sell me such a fish. I even made plans for a holiday to Mauritius, where this fish lives. At last, I was able to buy this one from a fellow reefer who switched to a smaller tank, and this gem has been in my tank for about one month now. So far, it's doing just fine!

  • Regal angel, Pygoplites diacanthus - Another 'second hand' fish that was already in someone else's tank. I've bought these fish at the LFS twice. Despite the fact that they both ate like pigs, both died within two weeks. This one, however, has been in my tank for nearly two years now. He eats almost everything I offer straight from my hands. I have found that he is NOT totally reef safe! He has mowed down a rock full of blue/yellow zoanthids, and because of his antics, I've had to remove a large brown Tridacna clam, a red Blastomussa, a red Lobophyllia and a green Trachyphyllia.

  • 2 Flame angels, Centropyge loricula - As with the yellow tangs, I added a second (much smaller) Flame angel after a few years. These two have been co-existing peacefully for about four years now. They do something which appears possibly to be spawning, but I've never seen any eggs.

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  • 2 Cherub angels (above), Centropyge argi - These were already together in one tank at the store where I purchased them. I added them to the main display after letting them gain strength in a quarantine tank for about a month. They spawn from time to time, and I think I've seen eggs being released.

  • Sixline wrasse, Pseudocheilinus hexataenia - I added this fish about five years ago.

  • 2 False Percula clownfish, Amphiprion ocellaris - This pair has been with me for roughly four years now, and they spawn every few weeks.

  • 2 Yellowtail damsels, Chrysiptera parasema - They are very territorial and don't like each other one bit. Both fish claim their own half of the tank and fight every now and then.

  • 2 Orchid dottybacks, Pseudochromis fridmani - I think they have spawned occasionally, but I'm not sure. I believe they are a mated pair.

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  • 14 Blue-eyed cardinals (above), Apogon leptacanthus - These are mouthbreeders and stay close together in a shoal most of the time. Typically, at any given time, one or two males are carrying eggs.

  • Coral goby, Gobiodon okinawae - This little fish hops from one coral to the next, protecting them against coral-eating fish. The downside is that it also feeds on some of the polyps.

  • 2 Blue mandarinfish, Synchiropus splendidus - I've kept the male of this pair for about six years now, and about two years ago I added the female. They spawn almost every evening. During this ritual I often notice them releasing eggs and sperm. The trick to keeping these fish is to provide them a tank which produces enough small critters for them to feed on. Unfortunately, I've never observed them taking any of the prepared foods I offer.

  • Lawnmower blenny, Salarias fasciatus - This might be the coolest fish I have! He does a great job of removing algae and providing entertainment for the people who watch the tank. It is also the only fish I have named: Henk. This name is also getting established as the Dutch name for this fish!

  • 2 Sailfin blennies, Emblemaria sp. - I added these in June of 2004, but because they are so shy, I've seen them only a few times.


As stated before, I like to keep a mix of different corals. I think it is almost impossible to name all my corals. I've counted more than 100 species of SPS corals and about 20 species of other corals (buttons, leathers, gorgonians, etc.). I think a nice array of photos says more than a list of species. I acquired most of the corals as small pieces or by trading with fellow hobbyists for coral fragments. I make between 100-200 small- to medium-sized fragments annually. I have some special species that I'd like to emphasize:

  • Yellow scroll coral, Turbinaria reniformis - I acquired this coral seven years ago, and it was almost dead. The size of the remaining live tissue was about 1." It cost me only two €uros. I removed the dead skeleton, and as you can see, the result is great! I'm very proud of this coral.

  • Acropora sp. (formosa?) - Located in the upper left corner of the tank. The mother coral was imported about ten years ago. I obtained a fragment of this coral from my local fish store. It grows like a weed! If I remember correctly, about 60 fragments were taken in 2004! Even after all the fragmentation, the size of the colony has increased enormously. Compare this picture to the overall picture of the tank at the top of this article. The first photo was taken in November 2002, the second in December 2004.

  • Pink birdsnest coral, Seriatopora hystrix - In 1996 almost no one in Holland had birdsnest corals at all. Then, I received a phone call from my local fish store wherein the owner told me they received six S. hystrix, one of which was pink. A few days later this coral was in my tank. Now, about nine years later, I still have this coral, and I've traded many of its fragments.

  • Pink/Purple tabletop coral - The owner of the LFS gave me a fragment of this coral. At first, it just grew like a bush, and one of the branches started to grow as a table. I fragged this branch, and it continues to grow like a table!

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  • 2 Blood shrimp, Lysmata debelius

  • 2 Cleaner shrimp, Lysmata amboinensis

  • 2 Peppermint shrimp, Lysmata wurdemanni

  • 2 Sexy shrimp, Thor amboinensis

  • 4 Red-legged hermit crabs, Paguristes cadenati

  • 1 sandsifting sea star, Archaster angulatus

  • 3 sandsifting snails, Strombus fasciatus

  • 3 unknown serpent stars with 'bold' arms, these are also safe with small fish (Ophiolephis sp.?)

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The tank is an all-glass tank of 130 x 70 x 70 cm, containing about 160 gallons. The front viewing pane is made of a special kind of glass called optiwhite. While normal glass has some green tint, this glass is as clear as acrylic yet has the advantage of not being as sensitive as acrylic is to scratching. It scratches more easily than normal glass, though. Located directly under the tank is a sump which contains another 35 gallons of water.

I also have a small tank of 50 x 30 x 30 cm connected to the system. This tank is not often used, but I put some new arrivals into that tank to let them relax from transport and gain some weight. I mostly do this with small fish for whom I expect problems from the existing fish population. Both cherub angelfish were the latest to spend a month in this small tank.

Main Circulation Pump
The heart of the system is a Red Dragon 10,000. I wanted a silent pump that doesn't draw much electricity but still moves a considerable amount of water. While this pump is almost completely silent, it pushes roughly 10,000 l/h but uses only 98 watts! This pump is also the only means of circulation in the tank. In my opinion it is very important to have as much flow as possible between the sump and the tank, thus making it possible for the detritus to reach the skimmer and be removed from the system.

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Trace Elements
I use a three channel Trace-el-controller by Grotech (seen below) to add trace elements. Grotech formulas A, B and C are added at a dosage of 4 ml each day. I've tried to add more or less, but varying the amounts reduced the corals' colors. I've also tried some other brands of three-formula additives, and I even tried mixing them myself. So far, I haven't been able to beat the results I've seen with Grotech. Sometime in the future, I might try the Zeovit method, but I'm still debating its use. At this moment I also currently use Salifert Amino Acids, and I believe that some corals show better colors as a result.

Water Top-off and Calcium Reactor
I use an automatic water top-off system with reverse osmosis water and synthetic sea salt. I mostly use Reef Crystals salt, but every now and then I use some Instant Ocean or Sera. I also intend to try Red Sea salt at some point in the future.

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I add calcium via a custom-made calcium reactor (above right) from my local fish store. I modified this reactor by adding an injector which recirculates the excess carbon dioxide. Using this method, it is possible to add much more calcium with the same reactor. This reactor is not computerized and runs continuously. Coarse coral is used as the media in this reactor.

Light is provided by an Aquaspacelight with two 150-watt HQI bulbs and two 24-watt power compacts. The fixture is about 5"above the water's surface. The HQI bulbs are BLV Hitlites; the power compacts are typical blue bulbs from Osram. I change the bulbs yearly. The HQI's are on for 12 hours/day, and the power compacts for 13 hours. I've been using 150-watt HQI bulbs for about nine years now, and I'm very satisfied with this way of lighting the tank. In the very beginning I used 6500K bulbs, because nothing was available with a higher Kelvin rating. Later, I switched to Aqua Medic 10,000K bulbs. This year, I decided to try the BLV bulbs. These bulbs weren't developed particularly for our hobby, and compared to the Aqua Medic bulbs, they lean a little more toward the blue part of the spectrum.


I use a Schuran Jetskim 150 skimmer. According to the manufacturer this injector-powered skimmer is able to clean 1000 L of water. It removes quite a lot of waste. Every now and then I use some ozone (50 mg/h) for a few hours to 'burn' excessive yellowing components from the water. I also use activated carbon. I put the carbon in a mesh bag; most water leaving the skimmer passes through this bag. I use about one coffee cup full of carbon, and change it when I think it is necessary, typically after about six weeks.

Water changes are also very important, in my opinion. I use no other filtration. In the past I've also used filter floss and I've tried zeolites but I've since decided to try to keep things simple. Since I removed the filter floss, the skimmer produces more waste. In the beginning I had more particulates in the water, but now the water is as clear as it was originally.

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  • Daily: overall checkup on the equipment for proper operation and the animals are checked to determine if they are all present and healthy. I also feed the fish almost daily. Sometimes when I'm not home for a day they have to find their food themselves. I think feeding is underestimated. When I compare aquarium fish to fish in nature, the fish in nature look fatter and healthier than most fish I've seen in aquaria. I feed the fish OSI Spirulina flakes and Duplarin granular food daily. I also feed dried Nori-flakes daily; the Regal angel and the Gem tang eat this from between my fingers. At least once per week, I add vitamins to the food. I also feed frozen foods every now and then: krill, Mysis, Artemia, chopped mussel, etc.

  • Every few days: clean the collection cup of the skimmer, clean the glass with an algae magnet, and fill the top-off tank with fresh RO water. Dislodged corals are returned to their original positions as noticed, but I try not to reach into the water unless absolutely necessary. I also use a pair of long tweezers and a PVC rod as tools to reduce the time my hands are in the tank.

  • Every two weeks: I perform 15% water changes with fresh synthetic saltwater. I vacuum the sand and suck away detritus and unwanted algae. I also clean the glass with an algae scraper to remove harder algae such as calcareous algae. I let the skimmer suck up one liter of vinegar-laden boiling water to remove dirt in the injector. After performing this procedure, I see an increase in the skimmer's performance.

  • When needed: cleaning the skimmer, making coral fragments. Additionally, the sand is replaced every so often.

Water Parameters:
I'm not an aquarist who measures very often. Here are some of my parameters:

Ca: 420 mg/L
Mg: 1400 mg/L
dKH: 8-10
pH: ~8.3
Nitrates: 0
Phosphates: 0
Temperature: 26º C (78.8º F)
Specific gravity: 1.0245

Problems Encountered:

After the tank was set up, I battled the bubble algae, Valonia sp. I tried to maintain good water quality, and I added a Foxface fish, Lo vulpinus, to remove these algae. The amount of Valonia significantly decreased. The Foxface wasn't totally reef safe, though; when he started scraping tissue off the Acropora, I returned him to the local fish store.

On my previous tank I used a very good skimmer which was connected directly to the overflow. Because the stand of the new tank wasn't as high as the previous one, it wasn't possible to direct most of the water through the skimmer. The skimmer didn't work very well anymore, so I added a Schuran Jetskim 150 which took quite some time to start working. In fact, the tank was almost skimmerless in the beginning and I do not recommend that.

Future Plans:

Because I think a more powerful skimmer would benefit the system, I've ordered a new skimmer, a Bubble King Intern 200 by Royal Exclusiv. This skimmer should be able to remove more waste than the current one does. Waste removal is very important for a tank like this, containing both a high fish load and a large population of SPS corals. I also expect to need a skimmer with some more muscle because of one of my future plans.

Breeding and Fragment Growout Tank
Quite a few fish spawn in the tank, and I regret the fact I've never attempted to catch or raise any of the fry. Thus, I'm toying with a plan to try to hatch some of the fry. I'm busy designing a sump which incorporates both a fragment growout tank and a fish growout tank. I prefer a 'clean' look in the tank itself, and in my opinion dozens of frags don't fit well with that look. I intend to light the growout tank with a couple of T5 bulbs. My goal isn't to raise hundreds of fish yearly, but if I could just raise one or two, I would be very proud! Of course, raising more than just one or two would be nice!


I want to thank Reef Central for honoring my tank with the Tank of the Month award. I also want to thank my fellow aquarists around the world for giving the advice and inspiration which have made this tank what it is today.

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Feel free to comment or ask questions about my tank in the Tank of the Month thread on Reef Central.

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Tank of the Month - February 2005 - Reefkeeping.com