Hobbyist Profile: Thomas Siodmok, a Conservation-Minded Aquarist

Author: Iggy Tavares

After designing his own dream reef tank, one innovative aquarist is using it to propagate corals to help the environment.

A New Challenge

Thomas Siodmok from Duisburg in Germany had been keeping freshwater fish for a very long time when, some five years ago, he decided he wanted something much more challenging and decided to move to marine fishkeeping.

In those days, he did not possess a computer or even have access to the Internet, which in some ways made gathering information about marines a little difficult. He had to resort to the good old-fashioned method of reading books. He was lucky enough to come across the six-volume set of The Modern Coral Reef Aquarium by Svein A. Fossa and Alf Jacob Nilsen (Birgit Schmettkamp Verlag, 1996), which he highly recommends.

The Setup

Having read the books, Thomas decided to design his first large marine aquarium himself, as in those days there were no other marine hobbyists he knew in his area that he could call upon for help. He made some drawings to scale for his approximately 250-gallon, 200 x 60 x 70-cm (75 x 25 x 30-inch) aquarium and its sump and gave them to a glazier for production. The cabinet for the large aquarium was also designed by Thomas, but he, being a good craftsman, actually built this himself.

All the installation work was also planned and done by Thomas, which was no mean feat, as the sump and other ancillary tanks are all downstairs in the cellar while the show tank is in his living room on the ground floor. This meant laying down a lot of piping to transport water around the whole system.

He introduced live rock into the aquarium, which went through a maturation period of around 12 weeks, with regular water changes until the water parameters started stabilizing. The waiting time could have been reduced substantially if he had used cured live rock, but he could not afford the price of $8 to $10 per pound for the 80 pounds of live rock in his system, so he bought less expensive rock that needed curing.

Adding Livestock

Algae Control

In the beginning there was a very strong growth of algae, which worried Thomas as he tried to figure out what he was doing wrong and what he should do to counteract this problem. From the books, he learned that some species of surgeonfish are fairly robust and can be introduced to marine tanks for the purpose of controlling algae. He found that worked as a solution to his problem.


When it came to first corals, there were no half measures here, as Thomas’ selection included hard corals such as a mushroom coral Herpolitha limax, a trumpet coral Caulastrea curvata, brain coral Cynarina deshayesiana, and a net coral Alveopora tizardi, while first soft corals were a finger leather coral Lobophytum sp. and Kenya tree coral Capnella imbricata. All these corals, apart from the net coral, are thriving in his show tank today.

Over the years, Thomas has carefully selected corals and anemones to add to his reef aquarium, not only for their lovely color, but also for their shape and form. He decided to go for both hard and soft corals, and anemones were chosen particularly for their swaying to demonstrate the harmonious motion of the water in the reef tank. Even some of the large-polyp stony corals have some long feeder tentacles that sway in the water as they try to catch tiny prey.

Today there are a lot of green-colored corals such as Euphyllia paradivisa, Galaxea astreata, Lobophytum sp., and Favia helianthoides, but all have different contrasting structures. Other colors include red, orange, purple, and cream. One of Thomas’ favorite corals is a large Catalaphyllia jardinei that he recently purchased.


Twenty colorful marine fish live in the beautiful reef aquarium and come in various shapes and sizes with their own particular way of swimming. For the most part, the fish are always on the move in search of something to eat. There are five tangs, including an Acanthurus achilles, Ctenochaetus tominiensis, and a Paracanthurus hepatus, all of which help to keep the aquarium free of algae, as they feed on it. Interestingly, they have a loose territory that they half-heartedly defend against each other by flashing their scalpel-like spines, but fortunately they do not damage each other.

Among the other fish, four different colorful dwarf Centropyge angelfish species that appear and disappear into the caves among the live rock also show some aggression toward each other. Thomas particularly likes to watch his three clownfish defending and caring for their anemone. He finds it very relaxing sitting in front of his beautiful reef aquarium watching the constantly changing activities of the huge variety of attractively colored animals that are always on the move.


The daily routine for keeping the whole reef system in optimal condition takes about half an hour and involves checking to ensure that all the equipment is functioning as it should, and that the pH and temperature readings are in the appropriate range. Fortunately the top-off system to make up for evaporation loss is automatic, but it still needs visual inspection daily.

Water Parameters

It is also necessary to check that all the fish and corals are healthy. Water parameters are tested and the protein skimmer is cleaned once a week. New water is prepared using an ion exchange unit, and the appropriate amount of marine salt is added for a 10-percent water change that is done every two weeks.

Feeding Fish

The animals in the reef aquarium receive a mixed diet consisting of 70 percent frozen foods, 20 percent algae, and 10 percent dry foods. The frozen foods consist of Artemia, mysis, krill, and chopped prawns, while the algae foods consist of nori seaweed, spirulina, and red algae. All of these foods are eagerly taken by all the fish, as well as shrimp, starfish, and clams. Although the fish take the lion’s share of these foods, a sufficient amount of this feed is taken by the corals and anemones, which are doing extremely well in Thomas’ reef tank. Even the reputedly difficult-to-keep copperband butterflyfish is doing well on this diet in this aquarium.

Feeding Corals

Corals and anemones do get a lot of their food from their symbiotic relationship with the photosynthetic algae zooxanthellae that live in their outer tissues. However, sun corals Tubastraea sp. do not have zooxanthellae and must therefore capture all their food with their tentacles. In the aquarium they do best if they are specifically fed, which is what Thomas does twice a week at night after the polyps open, using a pipette to feed Artemia and mysis. Although it does involve a little extra work, he finds this worthwhile because it ensures that the beautiful sun coral stays healthy and continues to grow in his aquarium.

Coral Propagation

Thomas does a lot of coral propagation due to his concern about collecting too many corals from the wild. It is also a great way to subsidize his hobby. The corals produced this way are also healthy and acclimated to life in the aquarium.

Water Conditions

To propagate corals, Thomas believes that one must create excellent water conditions, which is not that simple. Excessive amounts of nitrate and phosphate can interfere with coral propagation, but chemical media can be used to remove them. If the nitrates and phosphate levels are near zero, then one can hope to be successful with propagation.

Propagation Tank

The coral propagation tank (60 x 15 x 16 inches, 60 gallons) is in the cellar and is well lit with four 80-watt T5 bulbs. It has good water circulation provided by three pumps. It is connected to the sump and protein skimmer that removes harmful nitrogenous waste that would stunt the coral growth. A Pacific blue tang helps to keep this tank free of any algae.


For coral propagation, Thomas takes coral fragments of 2 to 8 cm (¾ to 3 inches), according to the type of coral he is propagating, from his main reef tank. The fragments are made using a pair of coral clippers for the hard corals, although some are easily broken off by hand. Leather corals, on the other hand, are prepared using a scalpel. While the stone coral fragments are ready for propagation immediately, the leather coral fragments have to be maintained in high-quality water with a current for several weeks to give the wound a chance to heal before they are ready for attachment to some rock.

Thomas prepares special attachment discs made out of coral sand and cement that are given at least 24 hours to set. For gluing of the coral fragments to the disc, he uses a special coral epoxy glue that comes in two parts and needs mixing together prior to use. The end of the coral to be attached is gently patted dry with a paper towel. The glue mix is applied to the coral end and also to the dry disc, and the two are brought together and allowed to set for a few minutes. After attaching, rinsing the coral fragment and disc in some marine water before placing it in the propagation tank stops it from clouding the tank. After a few weeks, coralline algae grow over the glue and it is no longer visible.

The growth rate of the fragments varies greatly from species to species. Many corals, particularly hard corals such as Acropora and Montipora species, as well as many large-polyp stony corals, grow very slowly. Naturally, the slow-growing corals fetch a better price.


Thomas maintains a good level of calcium (410 to 430 mg/l) and magnesium (1300 to 1350 mg/l) in his water by dosing with metering pumps from a stock solution. Special trace elements are also dosed every two hours, all of which help the corals to grow at the maximum rate and have beautiful colors. Coral fragments can reach a saleable size of 5 to 10 cm (2 to 4 inches) within four to twelve weeks, depending on species. At this size they can fetch $15 to $25 depending on species, which can then be used to buy other large, rarely seen corals, such as his Catalaphyllia jardinei.

A Homemade Reef

Thomas set up his stunning reef aquarium after a period of research performed largely on his own, which makes it a real achievement. Today, his large, perfectly run aquarium is brimming with more than 90 different species of colorful hard and soft corals, as well as zoanthids and some anemones.

Although the corals are in close proximity to each other, there are no obvious problems of coral aggression as of yet in this aquarium. Thomas also has a nice balance of fish in his reef aquarium, with the larger colorful tangs and surgeonfish typically upfront on display. The smaller angelfish, gobies, filefish, puffer, and more are also very active but dart in and out of caves, adding an edge of intrigue to this reef aquarium.

Thomas does have a passion for colorful corals and is able to identify all members of his collection by their Latin names. He is a conservation-minded reefkeeper who realizes the importance of minimizing the collection of corals from the wild and has set up a highly successful coral propagation unit.

Although the unit is not large, he maximizes coral propagation by having five glass shelves in the aquarium to carry well over 100 growing corals. High calcium, good light, and water circulation ensure that coral growth is optimal. Thomas Siodmok sets an excellent example for other reefkeepers to follow.

Water Parameters

Ca: 410 to 430 mg/l

Mg: 1300 to 1350 mg/l

Sr: 8 to 16 mg/l

KH: 7 to 8

pH: 7.9 to 8.3

Redox: 280 to 350

PO4: 0.005 to 0.01mg/l

NO2: 0.00 mg/l

NO3: 0.00 mg/l

Si: 0.00 mg/l


  • Acanthurus achilles
  • Acreichthys tomentosus
  • Amphiprion ocellaris
  • Canthigaster valentini
  • Centropyge bicolor
  • Centropyge bispinosa
  • Centropyge ferrugata
  • Centropyge loricula
  • Chelmon rostratus
  • Chromis atripectoralis
  • Ctenochaetus tominiensis
  • Doryrhamphus excisus
  • Paracanthurus hepatus
  • Pholidichthys leucotaenia
  • Pseudocheilinus hexataenia
  • Pseudochromis fridmani
  • Zebrasoma flavescens
  • Zebrasoma xanthurum

Anemones, Zoanthids

  • Actinodiscus sp.
  • Condylactis gigantea
  • Entacmaea quadricolor
  • Parazoanthus sp.
  • Phymanthus buitendijki
  • Various Discosoma spp.
  • Various other Zoanthus spp.
  • Various Protopalythoa spp.
  • Various Rhodactis spp.
  • Zoanthus pulchellus

Soft Corals

  • Briareum asbestinum
  • Capnella imbricata
  • Cladiella sp.
  • Clavularia viridis
  • Knopia octocontacanalis
  • Pachyclavularia violacea
  • Sarcophyton ehrenbergi
  • Sarcophyton trocheliophorum
  • Tubipora musica
  • Two Lobophytum spp.
  • Xenia umbellate

Large-Polyp Stony Corals

  • Australomussa rowleyensis
  • Catalaphyllia jardinei
  • Caulastrea curvata
  • Caulastrea echinulata
  • Cynarina deshayesiana
  • Cynarina lacrymalis
  • Euphyllia ancora
  • Euphyllia divisa
  • Euphyllia glabrescens
  • Euphyllia paradivisa
  • Euphyllia paraencora
  • Favia sp.
  • Favites sp.
  • Fungia scutaria
  • Fungia sp.
  • Galaxea astreata
  • Goniopora djiboutiensis
  • Herpolitha limax
  • Hydnophora exesa
  • Hydnophora grandis
  • Mussa angulosa
  • Pavona cactus
  • Pavona decussata
  • Pavona frondifera
  • Scolymia australis
  • Scolymia vitiensis
  • Symphyllia valenciennesii
  • Tubastraea faulkneri
  • Turbinaria mesenterina
  • Wellsophyllia radiata

Small-Polyp Stony Corals

  • Acropora cytherea
  • Acropora echinata
  • Acropora granulosa
  • Acropora horrida
  • Acropora kosurini
  • Acropora millepora
  • Acropora nana
  • Acropora nobilis
  • Acropora parilis
  • Acropora pulchra
  • Acropora sarmentosa
  • Acropora tenuis
  • Acropora tumida
  • Acropora vaughani
  • Acropora yongei
  • Five forms of Montipora digitata
  • Montipora caliculata
  • Montipora delicatula
  • Montipora effusa
  • Montipora foliosa
  • Montipora hodgsoni
  • Pocillopora damicornis
  • Pocillopora elegans
  • Seriatopora caliendrum
  • Seriatopora hystrix
  • Stylophora subseriata
  • Tricolor Acropora

Other Invertebrates

  • Calcinus latens
  • Calcinus elegans
  • Calcinus tibicen
  • Lysmata amboinensis
  • Lysmata debelius
  • Ophiarachna incrassata
  • Ophioderma longicauda
  • Tridacna crocea
  • Tridacna maxima

See the full article on TFH Digital http://www.tfhdigital.com/tfh/201010/#pg99