Setting up a 500 L discus tank

by Babis Tsokas

I was always interest in the setup of tanks irrespectively of the final result which may or may not satisfy my aesthetics. The whole process from planning to the little details and tips of the project was full of information which solved problems or gave rise to issues which should be dealt with in the future. This interest helped me to decide to present the process of constructing and operating my 500 L tank which houses discus.

The whole process was the result of my desire to keep discus, which haunted me ever since I entered the hobby. Since I knew that keeping them asked for knowledge and experience I decided to wait for a couple of years before giving it a try. During this period I spent a lot of time with Andreas Kamarinos (Hydrocosmos) discussing tank sizes, various equipment, as well as the provisions one should make before starting this project. After some time, taking into consideration every possible alternative, we finally made our mind and came up with a glass tank measuring 150x70x50cm (LxHxW), with six holes which would be used to connect the overflow as well as the inlet and outlet of the filters and the waste pipe.

The final location of the tank was already decided - it would stand in the place of my smaller 60 L community tank (photo 01). The first item to come in place was the metal stand. This was an especially sturdy construction, perhaps more than was actually needed, with the same dimensions as the tank to be placed on its top and a height of 70 cm. It was made from metal bars with a 4x4 cm crossection. After I applied a coat of anticorrosive paint and a second coat of black paint, I added some plastic pads (one under every leg) as well as shelves made of black melamine, which would hold the supporting equipment. The stand was now ready to welcome the tank which came in a few days later (photo 02).

As soon as the tank came home, my first impression was that it was a huge tank (this is always the first impression). While enjoying this feeling of satisfaction I started working on it. The first step was to put the adhesive background in place (photo 03). This adhesive can be purchased from stores selling signs for shops (the kind which is lighted from the inside). Its price is correlated to the length you will need and is available in a large range of colors. Its main advantage is that it will attach firmly and completely on the glass without the usual air pockets humidity can't enter between it and the glass creating the ugly look commonly seen when posters are used instead. Following that, I added the connectors at the back and the bottom, the outlets and the overflow which would drive water in the sump (photo 04, photo 05, photo 06, photo 07).

Next came the leak tests. As is always the case, some small leaks (at the joints of the outlets) were observed which were fixed. Then the system was theoretically ready to by used. In theory, because in practice there was still too much to be done. The main issue was - naturally - the wooden cabinet which would cover the metal stand.

Waiting was a must since it would be impossible to move the tank and the stand when filled with water. I chose9 mm thick plywood as the material for the cabinet since it is known to have a high resistance to humidity. I applied an extra coat of varnish for additional protection. This particular varnish mimicked wood fairly well but.. there was a problem. There were some holes drilled on the cabinet which would allow it to be secured on the metal stand. Those holes were covered with putty which was not covered by the varnish and the overall result was far from satisfying. It tool me a lot of time and research to find the right stuff (I didn't have a clue what to use). In the end, I managed to find a special varnish which could be worked with a brush and mimicked wood very well.

Last came the three doors which would allow access in the space under the tank. They were made of the same material (plywood) with a different thickness (18 mm). The stand was now ready and the tank was moved to its final location. Sixty Kg of quartz sand were added (very fine grain), three large pieces of bogwood (after treating them), water (absolutely necessary) and then the filters were started. Cycling had started - at last..  (photo 08)


Filtration was performed by two Eheim 2217 (1000lt/h each one) filled with a total of 10 Kg of biological substrate (EHEIM EHFISUBSTRAT) as well as a 60 L sumo with 4 compartments and an EHEIM 1250 water pump (1200lt/h) (photo 09, photo 10). The two middle compartments of the sump were filled with sponges with different size of openening (30, 20, 10 ppi), mainly to collect floating particles but also to be colonized by bacteria (photo 11). The water enters the sump at the right most compartment as you can see in the picture. When the first compartment is filled with water, the water is directed at the sponges following the direction of the arrows in the photo. The bottom of the two middle compartments of the sump is covered by the white plates with openings which are used in undergravel filters. In the fourth compartment the water pump sends the filtered water back to the main tank. In the first and last compartments a 300 W is placed. Last, there is an overflow located at the top of the first compartment which is used to remove water during water changes  (photo 12). Although I have repeatedly calculated and tested the capacity of the sump to make sure that it is able to accept the extra water from the main tank in case of power failure, this overflow is an extra protection apart from being extremely handy during the regular water changes.

(photo 13) The inlets of the two kanister filters is at the bottom of the aquarium - in the middle(1), one of them has its outlet also at the bottom of the aquarium - at the left part (2), while the other in the upper part of aquarium, at the right side, next to the overflow (3). The sump has an inlet coming from the overflow by TUNZE (1500lt/h) at the right side of the aquarium (4), and the outlet at the top left side (5). At the right part of the aquarium bottom there is a sewerage for the fast removal of water (6), while the sump has its own sewerage, which is linked with the one coming from the tank and leads to the balcony via a permanently fixed plastic pipe (Φ40) (photo 12).

The lid was made last since I wanted to be sure about the water level with the sump in operation. I do not like the line of water level to be visible under the lid of the aquarium, so I wanted to be sure that my construction would cover it completely. A second element that was very important for the design, was my wish to have a lid with a minimum height. I have always disliked the sight of canopies which had a height almost equal to half the size of the aquarium itself and this was something I would really like to avoid. Keeping those two thoughts in mind, taking functionality into account as well as using the experience I had acquired by building canopies for two more tanks I was ready to materialize my project. I must confess that I also searched the web and saw some solutions used by other hobbyists to solve the same problem.

Plywood (9 mm thick - as the one used to cover the stand) was the material of choice once more and the final height of the canopy was a mere 8.5 cm (thanks God). It has two openings at the top and a vertical joint in the middle.

In detail, I used a simple lath (cross section: 1x1 cm) which rested on the edge of the glass tank creating the perimeter of the canopy from the inner side (photo 14). The edges were cut at a 45 degree angle although this is not necessary. Next, the two sides, with a height of 8.5 cm and a length equal to that of the glass tank (150 cm) were glued on the wooden perimeter described above with special glue for wood, while small nails (those which lack a head) were used to ensure maximum stability of the whole construction. They were placed in such a way to leave a space of 1 cm so, when the top covers would close, they wouldn't be visible from the front side of the tank. This was also one of my ideas, since I had noticed that lids which close on top of the canopy always allow some light to escape while they are aesthetically inferior. 

There was a gap at the edges of the side panels of the canopy (photo 15) which was covered with a special, "rounded" piece of wood. The result was a seamless, rounded corner (photo 16).

At the back of this frame I fixed permanently, in the same manner, a panel; this rests on top of the back part of the frame. The length of the panel is 150cm (the full tank length) while its width is 8,5cm. The panel supports the two top openings thus allowing for easy access to the tank. It doesn’t get in the way as it is placed over a 10cm stake. A 6cm wide joint, permanently fixed, connects the front to the back part of the frame for added stability. I then secured  the two covers of the top openings in place (72x41,4cm). These are fixed on 4 hinges each which allow them to open and close (photo 17). This brings us to the last detail of this construction, namely the back openings. These openings are used to feed through the lighting cables. They also accommodate the joints from the return pipes (photo 18). It is important to note that the construction should be such as to allow for the lid to be easily removed, without being hindered by anything else (photo 19).

After completion of the construction, putty was added at the edges which were smoothed with sandpaper and painted with three coats of a wood-like paint, the same used to paint the cover of the stand (photo 20).

Next step was to add the light fixtures and the necessary connections and wiring. Three T8 fluorescent tubes (120 cm each)  were selected. Two of them were white (Arcadia Freshwater) and one with a slight pink color (Arcadia Original Tropical). They rest on thin (2 x 1 cm) aluminum racks so they can be moved easily back and forth and are powered via watertight end caps made by Arcadia. The transformers and starters are located under the tank along with the other electric components (multiple sockets, timers etc.) (photo 21). The duration of the light period has been set to 10 hours for all three lamps while one of them (the pink one) is turned on half an hour before them and turns off half an hour after them (11 hours in total).

The first fish to inhabit the tank (six months had already passed since the tank was received !!) were a school of 10 Corydoras sterbai, 2 Sturisoma Aurium and a small Ancistrus sp. which lived in one of my old tanks. Unfortunately, after two days I lost 2 of the C. sterbai which were stuck in the filter inlets (that I had not covered till then) and one of the S. aurium (which was obviously weak and didn't make it). A month later, a school of 30 Hemigrammus Βleheri was added.

I wanted to stabilize the system as much as possible, find solutions for all the maintenance routines of the tank, resolve any issues which might rise at the beginning and then add the discus (for which this whole system was set up). This took another 9 months !!

One of the most important issues that I had to deal with was the water quality, its preparation and the (frequent) water changes. The obvious solution was to get a reverse osmosis unit but the fact I would throw away three times the volume of water I would use forced me to reject it - at first. After some research I decided to buy a deionization column. The specific model I got has a capacity for 1200 L of water with a GH=8 and can deliver 10L/min of deionized water. This column contains a mixed bed of resins and absorbs all ions dissolved in water as well as traces of F, Cu and more. Although I had my doubts at the beginning, a recently calibrated monitor showed an indication of 0μS at its outlet. Pure water ! (photo 22, photo 23)

The column was placed behind the refrigerator and the water, after deionization was stored in an 100 L tank (70x55x30 cm) which is located in a cabiner under the kitchen pass. The pass is next to the tank so I can use a water pump (1000 L/h) to send the "prepared" water (75% deionized - 25% tap water) in the tank (photo 24, photo 25, photo 26).

Things seemed to be in order now and after checking the water paremeters for some time (photo 27), I started my investigation about the discus "species" which would get into the tank, as well as which would be the source for my fish. I used the singular form because my intention was to get only one type of discus. In general, I don't like the "color sampler" type of tank, in which you can see red, yellow, green and blue fish. Apart from that, I wanted all the fish which would be added in this tank to be adults, of similar size and to add them all at the same time (for obvious reasons). Finally, I decided that I would keep six fish while I asked for (and got) a warranty that these would be 3 male and 3 female specimens. The discus type was "Brilliant Turquoise" by the well known German breeder Jorg Stendker.

The order was placed and - finally - the box with the fishes arrived !!! (photo 29). I had already made my preparations to welcome the newcomers. A large water change was made in the main tank, most of the glass surface was covered with black nylon bags while a 60 L tank was to be used for the acclimatization process. This was also covered with black nylon bags while a heater and an air diffuser (connected to an air pump) were placed inside (photo 30)

I opened the box and the bags which contained the fish in a room with low light levels to avoid extra stress of the fish. The bags were carried (opened) in the acclimatization vessel which contained a small quantity of water inside to adjust the temperature, which had dropped to 25οC during the transportation. I kept on adding a small quantity of water from the main tank in every bag and eventually I emptied the bags in the small tank  (photo 31, photo 32)

The paremeters of the water in which the fish were transported were pH: 7, GH: 18 and NO3: 20ppm. I went on adding water from the main tank to the small tank for a while. The whole acclimatization process lasted for 3 hours. The fish were then placed in the main tank, one by one. Although I expected all of them to run and hide being out of my sight for several days (I had already decided to keep the lights of the tank turned off for some days) they didn't. On the contrary they gathered together at the upper part of the tank which was not covered with black bags. They didn't seem to be frightened at all and they rushed to the front glass whenever they felt human presence, most probably in anticipation for food. (photo 33, photo 34) The German breeder had told me that adult discus can take 3 weeks or more before they accept food after being transported, without any adverse effect on their health. Thus, I didn't offer them any food for the first couple of days but since I saw this fearless and social behavior I decided to remove the bags and offer them frozen beef heart on the third day. 

Needless to say, they accepted the food greedily. After a couple of days I turned on the lights (gradually) and all of them seemed as happy as ever. I only refer to discus because the H. bleheri which were used to swim in there alone, were far less active, probably waiting to see how their new tank mates would behave.

After 15 days or thereabout, the first pair formed laid eggs and was faced with aggression of the rest. Long fights, fierce defend of the territory by the parents, attacks to destroy the eggs from the rest etc. (photo 35, photo 36). A few days later, a second pair was formed, which naturally claimed its own territory turning the tank in a war zone (photo 37). Well, you can guess the rest.. separators were added, the aggression was still high, problems because of the poor water flow due to the separators (along with the development of BGA)... this case looked more and more like... new tanks !

Some pictures of the fish taken at the beginning of 2006...
(photo 38, photo 39, photo 40, photo 41, photo 42, photo 43)


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