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Janne's Malawi Aquarium Background
(Starting The Malawi Aquarium)

[Editor's Note: This article appears in its original form on Janne's Website, and has been reproduced here with permission.]

I and my wife started a Malawi aquarium in June 1998. Since it required quite much planning and constructing compared to a usual freshwater tank, here is a small description of what I did for someone perhaps to get useful ideas.

1. Literature

Since the fish from lake Malawi have certain requirements concerning the water chemical composition and environment, for example, I advice to go through some literature first.

I surprisingly found one book about Malawi cichlids translated in Finnish, in addition to which I ordered three books from Here is a list of those books:

The English books are published by T.F.H. Publications, Inc, and the Finnish one by Suomen Akvaariopalvelu. If I should recommend some of those, I would now probably buy my books in the order given above. The book by Sweeney gives a general idea about Malawi aquaria with beautiful figures, while Ad Konings mostly presents systematically different species and their requirements (and with Finnish names!). The third book is quite like the first one, in both contents and quality. The book by Melke is also very good and it is the most complete presentation about the subject, however I didn't like all of the ideas in it. Red gravel, miniature castles inside the tank, horrible space city background figures... I prefer natural biotope.

I also studied the possibility and ways to achieve the correct water chemistry. I called to the local water department, and they told that our pipe water had pH of about 8 and general hardness of 2,9 on the German scale, which values satisfied me. I decided that dolomite gravel and quite dense water changes are sufficient actions for the correct water quality, naturally in addition to filtration.

2. Hardware

For the aquarium system I bought the following components:

3. The background

As it is generally known, the mbuna fish of lake Malawi like rocky neighbourhood. It is recommended to fill the whole background of the tank, from bottom to top, with rocks to give mbuna caves to hide. However, since we don't have much lighter stones than granite around here, and since I was not satisfied about the idea of having hundreds of kilograms of stone in my living room (on a glass floor of the tank full of water), I tried to find out some lighter alternatives.

I got a hint of using pieces of coal instead of rock, I even saw such installation inside an aquarium. In fact, I suppose that that kind of coal is called anthrasite, which is the hardest type of coal. Anyway, coal is not used for heating here, and the only dealer I found did have only too small pieces of anthrasite. Let's emphasise that I am by no means sure if coal or anthrasite are harmless to the fish or not.

As a result, I decided to make the background of styrofoam (Styrox in Finnish). I asked for assistance via Usenet newsgroups, and Christian Hollman from Canada is acknowledged for his detailed instructions. My procedure loosely follows the one of him.


I started with a sheed of styrofoam, dimensions 1200 mm x 1000 mm x 100 mm. I sawed the sheet to three separate pieces, which together covered the background of the tank (with dimensions of 1300 mm x 520 mm). After that I cemented with silicone smaller pieces of styrofoam onto the shaped pieces (See figure on the right. All figures are thumbnails to bigger images). As a result, I had pieces with one to three layers of 10 cm each. I tried to shape the intersections between separate pieces and to position the cemented smaller pieces so that one could not see through the intersetions to the background glass or even outline the intersections.


As the second stage I cut holes to the styrofoam to get it look like rock formations. Especially I tried to get as many caves as possible. I also made some internal connections between the caves. I had two knives as tools: one with an 18-cm blade (called Lapin leuku in Finnish), the other with a 7.5-cm blade. With the longer one I could make some coarse structure, however the smaller one was very handy in digging small holes. Since I wanted to hide all the unnatural aquarium equipment, i.e. heater, filter tubes, thermometer etc., I also cut 60 mm x 60 mm vertical holes to both of the back corners. For the filter output I had to, however, make a hole that is visible from the front. In order to get enough circulation for the hidden heater and filter intake, I had to make many caves that have another opening to the "equipment rack".


On the left there are two figures of this stage. On the top one can see the structure from the front side, on the bottom from the back side. On the lower figure one can see the vertical holes for the equipment. On the other upper corner one can also see the hole for the filter output. I did the styrofoam shaping job in our bathroom. As a result I got one 150-liter plastic bag full of small chop, sticking to clothes and everything due to electricity.

After shaping the pieces I tried to smooth the surface in order to hide the styrofoam cellular structure. I used a hot air blower, which gave out temperature of about 500ºC. The result was not quite what I wanted. The styrofoam cells shrinked, but left the structure visible. I wonder if I had used a blow-torch, would I have received a better result? I did the heating of the styrofoam outside due to possible toxic gases.

Next, I painted the structure with a special latex paint. I wanted to use some toy-approved water-resistant paint, however the major paint pruducer that I contacted had usable paint only for industry use, sold in barrels. The problem with usual oil-soluble paints is that they dissolve also the styrofoam. In fact, someone told that local kids make napalm of their own with paint and styrofoam... Anyway, I had to use latex paint. I had taken care, of course, that the paint did not contain any toxic materials. I used three colours: black, gray and something between brown and red.

I don't expect latex paint to stay under water as the uppermost surface, because of which I used another layer on it. In order to get a hard surface that would save the styrofoam from being bitten away, I coated the surface with epoxy resin (epoksihartsi in Finnish). I was adviced not to use fibreclass resin, which as polyester-based will dissolve the styrofoam. Finding epoxy resin was a bit difficult, however I found one local company that uses it for repairing concrete structures. It was sold with trade name injection resin (injektiohartsi in Finnish). The resin was a bit costly (see below), because of which I bought only one liter of it. In fact, that was also the main reason for painting the structure before resin: I was adviced to coat the surface with sand and resin, but since I did not know how much resin it requires, I decided to be sure to get even some non-white colours without liters of resin. Getting in touch with the guy I bought the resin from required also some arrangements, and I did not want to disturb him several times due to my small amounts of resin.


Epoxy resin is two-component stuff and quite harmfull, I am told. It will harden after about 15 minutes from mixing, depending on the temperature. I mixed my one liter of resin in several portions, and used usual paint brush to spread it on the surface. I tried to be as accurate as possible especially in the case of caves. This stage I did also outside because of possible toxics, however I got some resin on my hands, too (and didn't note anything special in that). Once I panicked quite much, when I got a drop of resin on my eye-glasses, fortunately I could wash them early enough. When the resin was hardened, I made some new cycles with the resin, now throwing fine sand on the wet surface. As a result I got a quite realistic surface, more or less rock-like. I run out of resin, but with another liter of it I would have coated the whole surface with sand. On the right one can see the background after painting, resin, and sand. After this I tried to wash all possible chemicals from the structure with water.

Finally, I was able to put the backgroud inside our tank. I had started the background project even before getting the tank, with only dimensions available. When I received the tank, I met, however, one problem. Our tank had three strips of glass above the water surface holding the cover glasses. Two strips were in both ends of the tank. I had made vertical holes to the back corners so that I could not get filter tubes in, throught the glas strips! Furthermore, even though I had made my background in three parts, they were so huge in all dimensions that I could not get them in due to three glass strips. I had to remove two of the strips with a razor blade - this resulted five wounds into my hands. Anyway, I positioned the styrofoam to its place and cemented it with cilicone, and cemented the glass strips back, this time to positions where the tubes of the filter could be used. I had checked that those two strips were used only for holding the cover glasses and they did not have any structural function for the tank. Because of our vacation trip I left the silicone to dry for about one week, after which I filled the tank with water and left possible chemicals to dissolve for about two days. After that I started the usual aquarium water aging process with new water.


The figure on the right shows the background after filling the tank with water. If one looks carecully (perhaps clicking the larger image), the output of the filter can be seen on the upper left corner. Below the filter output is a small red dot, which is adjuster of the heater. Symmetrically on the right are intake of the filter and thermometer, which can not, however, be seen on the figure.

Today, it has been about four months since starting the system. Nowadays the background seems very realistic, that is even better than in the figure above, because of growth of green and red algae. At the beginning, since I did not have enough resin, one could easily see cellular structure of styrofoam in places where there was no sand but only paint and resin. Also, the intersections between the three separate styrofoam pieces can not be easily seen.

4. Materials

Here is a list of materials that I used for the background, in case that someone, most probably here in Finland, is looking for them. I can not guarantee that they are the best choices, or even safe, however in our tank everything seems to be running fine.

5. Expences

I will not cover cost of the usual equipment, such as tank, filter, stand etc., since those prices can be obtained from the local pet store. However, here is a calculation for the background:

During those days, USD 1 was about FIM 5.5.

6. What to do differently now?

I might study the use of anthrasite again, since the construction required dozens of hours, which I hardly had only during my summer vacation.

I would make a bit different kind of caves. My current caves are perhaps too open, and I would make smaller openings to them. I would also make more connections between the caves, since caves with several entrances seem to be most popular.

Now, after learning how to use epoxy resin, I would probably not use paint at all. Instead, I might just use resin and sand on the surface, since, as I learned, one indeed is able to fill the entire surface in that way and it seems much more realistic than paint. Anyway, now I have learned that even latex paint can be used, and after a couple months of algae growth that makes no big difference.

The water circulation is a bit problematic, perhaps due to the hidden filter input. I would study different configurations and their effects on circulation.

7. Later major modifications

December, 1998: In order to improve the circulation and to be sure about the water quality, I added another Project PJF 1001 external filter. This time I partly gave up the idea of leaving the equipment out of sight, and made another kind of approach: the output of the second filter is a horizontal tube with six holes at the left side of the tank, near the water surface. The ciculations seems very nice now.

Images and text on this page copyright Janne Jokinen 1998-
28.11.1998- (last modifications 20.12.1998)
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This page was last updated 18 February 2002