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Author: Michael "Arapaimag"
Title:  Building a Monster 50,000 Gallon Aquarium

Summary: Michael has gone where many serious aquarists would love to follow - constructing his own 50,000 gallon home aquarium! His ongoing recollection of the experience provides fascinating reading - whether you keep guppies or groupers!
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#373 - 5525 West Boulevard
Vancouver, British Columbia
V6M 3W6

Building a Monster 50,000 Gallon Aquarium

by Michael "Arapaimag"


Remember you are only restricted by the size of your dream. And I dream MEGA.


I built my mega 50,000 gallon and mini 15,000 gallon tanks in the 1994 to 1997 period.

My mega tank: I built the tank as an addition to the home and then joined it by putting doors through the basement and upstairs through the bedroom. You can see the excavator removing the soil on the first week of construction. You can see the doors cut through my walls in the 3rd picture.


A big aquarium needs a big space!


Preparing the groundwork

The lower section has my tank and in the upper section I keep my tropical birds. I had to do it on a budget so it is not fancy like a public Aquarium. It took me 9 years to save the money and 1 year from start to water in the tank. It is now in its 11th year with water. I was restricted in it being a beautiful landscaped tank because of my injuries. I am physically very limited and could not do much in its construction since I am paralyzed from the upper chest down.

The outline of the aquarium takes shape


I honestly only expected it to hold water for about 10 years, so I am doing better than expected. My large tank is L shaped. The long part of the L is 36 feet, the short part of the L is 27 feet. The front to back of the long part of the L is 18 feet, the front to back of the short part of the L is 15 feet. The tank water is 9 feet deep. In the picture below you can see a couple helpers installing the base plates for the angle iron, which were cemented (lower 4 feet) and formed the frame for the glass to be inserted.

I used 12" thick walls.

I used 3" square tubing and and I am sorry to say don't remember its thickness. A welder who had built large zoo type exhibits for alligators/crocs did the work and I relied on his judgement. He applied a rustproof coating to the exposed metal which was bolted to the concrete floor and the conctrete was framed around it to the height of where the glass started.


Reinforced concrete to hold many thousands of pounds of water pressure

In the design phase of this project I decided to build a 4 foot high wall inside the aquarium that would divide the tank somewhat. The wall serves several purposes: 1. It and the L shape reduce aggression by stopping eye contact at times among predatory fish. 2. It helps brace the tank 3. It allows me to drain one side or the other and just move fish into the side with the water in case I need to make repairs. The Aquarium holds a little over 50,000 US gallons. The floor area of the aquarium is 800 square feet. I only have glass on the top 5 feet of the tank and have a floor at that level so I can feed the fish etc., from my wheelchair. In this tank I keep many small cichlids, barbs and characins. I used 1" glass for all the viewing panels. I used regular glass because I was told it is stronger than regular laminated glass the same thickness. Laminated glass is recommended in situations where the public is involved due to the safety aspect of one pane holding should the first be broken/cracked.To get away with such a small thickness the panels are only 3 feet wide and 5 feet high. A viewing glass area was put into the ceiling of the aquarium so viewers could admire the fish from above. As well 11 skylights were put into the roof of the bird room above the aquarium so that beams of sunlight could come into the tank at different angles during the day. I put in two small windows above the water line to get some natural light. One facing south, the other north to get some natural light at those times. 

Initially I hinged one large glass panel to allow easy physical access to the aquarium to replace bulbs etc. via a rubber dinghy. Two problems arose from this. First, the glass panel 6x2 feet was too difficult too keep clean. Second, some of the fish bit the dinghy causing it too leak. My friend Dominic got his 6'3" 225 lb frame out of the tank fast ! The solution to the first problem was to replace the glass panel access door with a solid one. As for the second problem, I bought a British military dinghy made of material the fish have not punctured in the last 10 years (So far).

In the picture below you can see the depth of the aquarium taking shape.

A deep aquarium begins to emerge

Almost ready for the glass panels to be installed

The concrete I had sand blasted to remove imperfections and get a very smooth finish, then epoxyed and covered with two coats of a siliconed water proof paint. One problem I encountered was that the second coat of paint never adhered to the first properly; this caused the second coat to peel off over the years. The effect is a bit unsightly, but the tank does not leak (YET!).

Decorating the main tank with lava rock

In the picture above, a helper is putting lava rock into the tank. I intended the lava rock to create hiding spots for the many small fish (under 12") in the tank to avoid the serious predators and give their babies a place of refuge. It also creates a natural filter for the aquarium.

This was a good time to put the large pieces of driftwood in as well. Also the plumbing was installed. I had placed 4 swimming pool drains into the bottom of the aquarium and 1 swimming pool skimmer at the 9 foot water level. The driftwood had been soaked in my outside ponds for 3 to 5 years in preparation for use in this project.

Installing the 5 X 3 glass panels; GE 1200 silicone was used

My friend Dominic installed 6 sodium lights and 12 double fluorescent fixtures. I also installed 10 sets of halogen 500 watt fixtures, but removed them over the first year because of short bulb life. Notice the 2nd and 3rd pictures below. I have filled one side of the Aquarium to make sure there is no leakage at the 4 foot safety wall. IT WORKS !

The pictures below show the filling up process. It takes 7 days to fill. The Aquarium was filled and drained over 3 month period 5 times to insure any toxins were flushed out.


Looking good so far...


Looking even better...


Almost there...

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The tank is filled!

The green tinge to the water disappeared over the first year.

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A few years later and it is home sweet home!

At this time I am having problems with my steel above the water line rusting. I built 10 access doors to feed the fish etc. and they are rusting also. I had problems with the floor above the tank after the first year because the floor materials absorbed water and weakened. I then had to replace the floor. I heat my tank with a house oil fired hot water tank. I have used 2 swimming pool heaters before this. But I had many problems 1. the first one ran great for 5 years but it had been installed improperly by the seller and caused a fire. The second one was far too big and it started leaking in the boiler after 1 and a half years. I use a 600 lb sand filter on the mega tank, the natural lava rock filtration, I don't over feed and I do about 10,000 gallon water changes every week

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A pair of  Arapaima gigas, Pacus, a Giant Gourami and assorted Cichlisoma all happy in their new home


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Unfortunately I lost these two red-tail cats for an undetermined reason


The Filter

Since the tank has been running for such a long time I have changed the pattern of filtration and amount of water changes. I have been unsatisfied with the clarity the past year and will replace the sand and very likely increase the number of filters. I have had to feed the fish more than in the past due to adding 3 baby red tails (Now 28 to 33 inches) and my 3 baby AG's. (28 to 32 inches). Because of this the filter no longer does a good job. Also Ionizers will be added as will pre filters.

I get a lot of Malaysian livebearer snails, bones from the fish that I feed and some small pieces of lava rock clog up the filter baskets of the pumps.

Initially I used an indoor swimming pool oil heater (1994/5). Then a larger indoor swimming pool heater in 2000. The boiler rusted out in 18 months or so. Then a commercial apartment building sized oil water heater. Now I am switching to natural gas and using either a tankless hot water heater with an external heat exchanger or a boiler with an external heat exchanger.

I looked into solar but found it was not practical cost wise for this size of tank.

The most I have spent in one month for the entire house was $1,200 for oil (Have since switched to natural gas) and $1,200 for electricity. This was for the worst winter month ever. On average however it is only about half of that for each.

Originally I had 4 drains go to the filters. I returned water from the filters with a couple of 2" pipes. The overflow was strictly sending extra water added to outside ponds.

I've recently added another intake which is in addition to the 4 drains I had originally. The intakes go to 6 blue bag filters where I use 600 milligram filtration bags. I also have a second bypass straight to the pump in case the bag filters get clogged. The bag filters each have 2 pressure guages (the normal swimming pool type and a differential pressure guage) I use the 660 bag filters because their main purpose is to catch larger objects like snails, small pieces of lava rock and any pool liner pieces.

The 3 hp pump then pushes the water through two 600 lb sand filters. Where I have upgraded the sand with multidensity material. The sand filters work well and the multidenisty material reduces chanelling. The returns from one filter then goes through an upgraded Rinnai tankless hot water heating system with an extra external heat exchanger which then returns the water to both of my large tanks (the 52k and the 15k). The 15k overflows into the 52k and has its own filtration system seperate from the one I am showing using a 2 hp pump and an additional 600 lb sand filter. I also have a picture of the new thermostat and heater switches. The thermostat will keep the heat to within one degree of my set. I keep the tank at about 78 degrees right now because of my baby Arapaimas. They are 40 inches now and will get to 50 inches in about 6 months. At that point I will reduce the tank temperature as they will slow down their growth rate to about one half inch a month from the present 2 inches a month they are growing now (this is my rates of growth on previous pimas I have raised).

Michael's original filtration system

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Michael's new filtration system

filter2.jpg (50552 bytes)

New filtration system from another angle

The return from the other filter goes through 4 10,000 in line Aquarium ionizers for molecular purification from Eco Aqualizer .
The system works well...........the fish are happy.........which makes me happy.

My big tank has a low fish density and the 28,000 lbs of lava rock really assist the natural biological filtration

I live in the country and have several ponds on my property so the drainage is not a problem. I use my wells to refill the tanks.

By not feeding too often my tank can actually exist without any filtration from the sand filter at all. I have monitored my tank for a full 365 day period without any filtration. Just the airstone running. The fish were fine and I saved $1,200 in that period on the electricity bill by not running that particular pump & filter.

My 15K tank can not be left more than 4 weeks without running the filter (also a 600 lb sand filter with a 2 hp pump). The tank was not overstocked the first 3 years but now many of the fish have grown between 18" to 36" and it is now overstocked. I run a high pressure air line at 6 foot deep at all times. I give 4,000 gallon water changes on this one.

My electricity bill runs up to $1,200 a month to run my 123 tanks, heaters, lights (I use full spectrum with ultraviolet on most of my tanks and tropical birds), many pumps, 2 freezers and 3 fridges required to hold the approx 1400 pounds of frozen food I need to feed them. I also have several ponds one of which has a waterfall that is only 7 foot high but stretches across the pond about 60 to 70 feet and has 4 large pumps running the waterfalls. Due to the cost of running so many pumps (up to 3hp each) on this pond I have kept the number of hours they operate down.

The Fish


Some of my fish I have had for over 10 years and a few like the Wallego and 3 of the Collasoma are more than 20 years old. I actually have hundreds if not thousands of small fish in the tank who utilize the lava rock and their street smarts to survive and reproduce. This week I noticed a small shoal of baby Filamentosa barbs in the driftwood. There is a shoal of about 10 adult Filamentosa barbs who have been in the tank for several years.

I've got a few red devils in the 15k and they breed every two to three weeks and have a schoal of about 500 babies right now. The big Dovi acts as their bodyguard and helps keep the larger fish away. It lasts about a week before all the babies are gone and the cycle repeats.

The smaller species of fish breed, grow and are eaten just like in nature. I have individual small cichlid, barbs and characins that have been in the tank since it was first populated. Yesterday I saw a small shoal of guppies in the driftwood who are descendants of guppies placed in the tank in the 1994/5 period when I was first cycling the tank. It is exciting to see things like this.

I have attached a pretty poor picture showing some of the smaller fish including some barbs (Hampala macrolepidota) , characins, monos (Monoductulus sebae) , scat (Scatophagus argus), assorted cichlids and even a few goldfish.


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A mixed community tank indeed!


Big fish:

I had that infamous two foot black shark that hammered the arapaima and red tail cats that weighed as much as 90 lbs. While the Wallego hammered the shark and in turn the red tails beat up the 2 Wallegos. So somewhat of a balance except for the shark killing the arapaima and 3 of the red tails. In 2004 I had my dinosaur extinction where 50% of all large fish perished in a 3 weeks of hell. Nobody could identify what killed them.

The remaining red tails, 6 panagasius sanitswongi, planiceps, tiger shovelnose, some Collosomas etc perished.

However some of the Collosomas, the wallegos, Mystus , Nigers, Nile channel cat etc got ill but recovered. Of course the Shark came through without a scratch. I then in time added the 3 baby redtails and my baby arapaimas when they reached the appropriate size.

There are a few plecos in the tank up to 18" long.

My redtail cats eat plecos so I never get any really big ones.

I do have some fair size pacu. The biggest one weighs over 40lbs.

Small fish:

I had hundreds (and possibly over 1,000) of adult Protomelius similis that from 1995 to 2004 swam in huge shoals and probably represented about 75% of the africans in the tank. After the kill mentioned above occured the fish that survived changed the balance to 25% P. similis and as the fish repopulated the tank within 6 to 8 months to the same numbers as I originally had the P similis got wiped out to only a dozen fish. The barbs have remained somewhat constant and have reproduced.

I have include a few pics of the kill the first week. A friend named Bill Gibbons helped bring the fish out for me.

I find that cichlids 12 inches or bigger (there are exceptions) are hunted more so than the cichlids that are smaller and able to use the lava rock when warranted. I do have an exceptionally mean dovi that might make it mainly because it has put a hurting on a lot of fish that have grown big while they were younger.

The small fish survive and reproduce because they are very smart they use the 28,000 lbs of lava rock to hide in the big fish eat some but lose interest in chasing them all the time and catching so few.

The wallegos appear to be the most succesful because they ambush capture (They lie still like a rock and just open their mouth when the prey is in range.) They do will hunt when the lights are off and pick off pish that are in the 12" to 24" range at this time. (Lights are off only during a power failure occuring at night.)

Here is a list of most of the fish. Scientic names as given to me at the time the fish were acquired. Common names that most of my friends know them as.

Psuedotropheus aurora
Pseudothropheus Sp. callianos
Abramites solari(hypselontus) abramite
Anostomus trimaculatus anostomus
Cichlasoma argentea argent
neon blue
Melanchromis auratus auratus
Clarotes laticeps blue nile catfish
Ancistrus lineolatus bushy nosed pleco
Perrunichthys perruno chocolate sailfin
Colossoma brachypomum colossoma
Herichthys nigrofasciatus
convict cichlid
Mystus wyckii crystal eyed cat
Herichthys dovii dovii
Melanochromis johanni(chisumulu) electric blue johanni
Cyphotilipia frontosa frontosa
Labeotropheus fuelleborni fuelleborni
Triportheus angulatus
giant hatchetfish
Hampala macrolepidota hampala barbs
Panagasius sanitswongi imperial or emperor shark
Herichthys octofasciatus jack dempsy
Aulonocara jacobfreibergi jacobfreibergi
Herichthys managuense
jaguar cichlid
Julidochromis regani julies
Species 14 lake victorian species 14
Leporinus arcus leporinus
???????? martini red
Haplochromis mloto mloto
Mono Mono sebae
Cichlasoma nicaraguense nicaraguense
Pseudodoras niger
niger catfish
Astatotilapia obliquidens (zebra) obliquiden
Barbodes pinnauratus(barbus orphoides)
orange gill barb
Psuedotropheus zebra orange top zebras
Sorubimichthys planiceps planiceps
Hypostomus plecostomus
Labeo erythrurus (frenatus??) rainbow sharks
Protomelas sp. spilonotus tanzania red empress
Scatophagus argus red scat
Phractocephalus hemioliopterus red tail catfish
Aulonocara korneliae regal peacock
Osteoglossum bicirrhosum silver arowana
?????? silver crest peacock
Alunocara baenschi sunshine peacock
Pseudoplatystoma fasciatum tiger shovelnose
julidochromis transcriptus transcriptus juli
Walago leerii walago
Theraps wesseli wesseli cichlid
Psuedotropheus zebra zebra cichlids


Fish Stories

I have found black sharks are very dangerous to large fish once they get about a foot long. Beside the big black I also had a 19" gold one also. I tried him in the 50k+. The first 3 months were OK but after that the gold shark was chased whenever he tried to swim in open water. The 24-26" black never left him alone and caused big wounds/bleeding. He was caught in a lucky moment and put into a 500 with a 36"+ african lungfish and a 30"+ alligator gar. He recovered from the wounds then started sucking the scales off the gar and dug huge holes into the side of the lungfish.

He had to be removed and placed in a 180. Both his victims recovered in time.

The cichlids do swim in open water lots of time when I have several lights on in the tank. However they are much more cautious when the lights are dimmed. There are many other scfhooling fish in the aquarium under a foot long (ie african cichlids, barbs, monos,etc).

The 12"+ managuense never appears to be on the hunt in open water but probably captures smaller cichlids among the lava rock. The dovi I received at 7-8" from a DJ"s pet shop because it was killing everything put in its tank.

When I received the dovi I put him into a 180 with a young redtail (16"+-). I worked in the fishroom for about 15 minutes on other tanks and then happened to look over at the dovi's tank. He had ripped the much larger redtail to shreds. I quicky moved the dovi into a similiar sized tank with a 24"+ african lungfish while I berated myself for being so stupid.

I soon realized I was even dumber than I had imagined as the dovi then destroyed the lungfish in less than an hour. He absolutely ripped the lungfishes fins to bits. Damaged the sides of the big lungfish as though someone had tried to fillet him with a knife.

Quickly I moved the dovi to a 50 by himself. I then put medication in both the catfish and the lungfishes tanks and it took 4 to 6 weeks for them to heal and return to normal

This hobby can humble every aquarist (It has me, many times over).

In time I moved the dovi to the 50k+ where upon it's introduction, bit a much larger 12"+ alpha male oscar as he was released on his way down into the 9 foot depths. We just laughed this dovi is not scared of anything.

Within 1 week all five 12"+ oscars had disappeared (They had been in the tank since 2004). I believe the dovi must have chased the oscars out of their territory and left them vunerable to the big Wallego leeri and other predators.

It has been in the large tank about 6 months now and because of the wide open spaces it no longer attacks everything it sees. This dovi is one of the most evil fish I have ever owned. A Mystus(I believe it's Hemibagrus this week) nemurus I got at the 1990 ACA in Chicago and a Mystus (Hemibagrus this week) wyckii ranks with the dovi. I am sure the little dovi would destroy my old 22" dovi in the 15k if they ever met.


Looking back what would I do differently?

Doing it over I would not have built the bird room above the tank and I would have built the tank deeper (15 to 20 feet). If I had the resources I would have installed the glass on the 36 foot and 27 foot sides with the glass going about 10' tall.

I have reduced the amount of light to my tanks because most of my big fish do not like bright light. Hobbyists tend to forget that many of the fish we keep come from sources covered by jungles or black tanic induced water, where the fish don't get much light. They really are uncomfortable in the bright light that many hobbyists provide them with. I plan to write an article on how fish eyesight differs from human eyesight in the future and why many fish prefer low level lighting.

I really had expected problems would occur by now. When I see problems in public aquariums with their huge budgets and many years of experience, I feel lucky with the limited problems I have had so far. But I also realize that I will have major problems in the future and will not be surprised when they do come.

"Dream as if you will live forever, Live as if tomorrow will be your last."


Post script: To answer a frequently asked question, I actually designed the whole tank set-up myself and built it with the help of family, friends and acquantinces in related fields. I am physically unable to build much. I am however able to do a lot of the maintenace in aquariums less than 5 1/2 feet high.

I am not a structural engineer but fortunately an aquantaince is. So he prepared the documentation required by the building inspector and advised the builder of the concrete foundation what would be required. My son also was an engineering student at the time and he also looked into it. My financial advisor teaches a course on glass at a local university and advised me on the thickness of the glass required.

Please note that none of this article or pictures can be reproduced or used in any article or story without my verbal and written permission .

A video of Michael's incredible 50,000 gallon tank along with its arapaima gigas inhabitants can be seen at the following link: Monster Fish Keeper's Video Link