Wet Spot Tropical Fish Facebook link Wet Spot Tropical Fish Youtube link Wet Spot Tropical Fish Pinterest link

June 29, 2015

Welcome to the weekend, dear readers. 

For the final week of National Aquarium Month, we’ll talk about very large tanks and the so-called tankbusters.  Any of the fish from the last two weeks, of course, can be housed in larger aquaria, but it is not strictly necessary – therefore, no “small” fish will be mentioned this week.  These large aquaria, over 90 gallons, can be commonly seen in 125 or 210 gallon sizes, both of which are occasionally used for communities, goldfish, or specimens, but can range to homemade ponds housing goldfish or cichlids in areas such as Florida.  The limit to the size of an aquarium is mostly logistical, as well as structural.  Remembering that one gallon of water weighs about eight pounds, the consideration of force exerted both outwards and downwards by, say, a 500 gallon aquarium must be kept in mind when designing a large tank.

Unfortunately, for those curious about building these huge spaces, I’m not an engineer nor do I have any helpful hints on the matter – I would expect a sturdy structural frame at the corners of the aquarium would be required, in addition to very thick glass or plexiglass.  Most monster tanks need to be kept on concrete flooring, such as found in a garage or basement, to support their weight.

Some “Tankbuster” fish can be housed by a semi-average aquarist, but most are best reserved for professionals at aquariums and zoos.  Fish such as Gars, Pacu, Arapaima, Paroon Sharks and Channel cats should be entirely out of the question for the hobbyist’s home tank.  As much as one thinks they can house the fish until it grows, rehoming a fish of this size is likely to prove nigh impossible.  From experience, we often have hobbyists attempting to rehome Pacu through our store.  By policy, as a tankbuster of this size, we do not accept them as donations and refer any people looking to do so to our local zoo.  Unfortunately, our local zoo has accepted so many overgrown Pacu that they have no space to take any more – I dread to think of how these scenarios end, however, there is simply not enough housing out there for fish of this size.

Those that can and are occasionally housed by aquarists with the means include some of the following beautiful fish:

  • Tetraodon mbu “Giant/Mbu Puffer” - Full grown, these fish will reach 18-24 inches in length, excluding their caudal fin.  They are messy eaters and wasteful and, therefore, require weekly 50% water changes for optimal health.  They require a pricey diet including shelled foods such as mussels, clams and snails to keep their continually-growing teeth at a manageable size.  The minimum tank size considered for these fish should be 500 gallons, with 1,000 ideal.  A four foot deep tank with a width of four feet and length of eight feet seems that it would be a nice size for this fish, allowing ample swimming room and gallonage for their upkeep.  I’ve always thought this would be an excellent addition to the center of a basement library or bar.  Of course, the biggest draw of these fish are their amazing personalities – as they must be housed alone, one must be sure to spend plenty of time with the fish for the sake of socialization.  These beauties are known for learning the faces and voices of their owners, as well as interacting and, in the case of very tame specimens, accepting pets or belly rubs.

Tetraodon mbu

  • Potamotrygon magdalenae “Reticulated/Magdalena River Stingray” – These are a smaller species of ray but can still reach from 15 to 25 inches in width, depending on care and whom one asks.  I’ve found reports of specimens at 30 inches in width.  With their size alone, one can see that at least 30 inches of aquarium width and depth is required for the fish to turn comfortably, especially considering their long tail.  A similar tank to the one mentioned for the Mbu, about eight feet long and four feet wide, would work for a small stingray such as this, though depth is of much less concern as these fish spend most of their time at or under the substrate.  Rays are known to have an abnormally high bioload thanks to their unique osmoregulatory system (the system that allows them to process the minerals absorbed from the surrounding water and, therefore, need extra gallonage of water and very large, frequent water changes.  They are best kept alone as even the most peaceful fish can cause them to be skittish.  Stingrays are best kept as fascinating specimens and are definitely striking, but are not for the average hobbyist – they are often nocturnally oriented and can be quite sedate most of the day.  If you truly love rays, these fish are a real treat, but remember that a lot of space and work must be put into maintaining them.

Potamotrygon magdelanae

  • Osphronemus laticlaves “Red Giant Gourami” – For these two foot Giant Gouramis, your standard tank sizes simply will not work.  With such a long body, the comfort of the fish comes into question when it cannot simply turn around in the water column – imagine having to make a three point turn every time you wanted to go to the other side of your room!  Seriously Fish suggests an aquarium with bare minimum dimensions of six feet of length and two feet of both width and depth, allowing a full grown fish to just be able to turn in their home.  A greater width is definitely advised, though the length is appropriate.  Already we can see that, while not requiring quite the large tank of the Mbu or Ray, the Giant Gourami is still a very large and beautiful fish.  Like these other fish, these are high waste fish with messy eating habits and large water changes are a requirement for their continued health.  Again, as with the other fish, these guys can make excellent pets that will learn their owner’s face and voice and come to beg for food.  While fully capable of eating smaller fish, these are peaceful creatures capable of being housed in a large community, however, remember how much space you will need for any additional fish on top of these big beauties!

Osphronemus laticlavius

Now, with the fish out of the way, it’s the last segment in our National Rivers Month spotlight.  Our local rivers have seen their share of environmental trouble over the years, but we Oregonians have spent a lot of time and money attempting to repair our mistakes.  From fish spawning ladders to dam removal and volunteer watershed cleanup efforts, we’ve done our best, but sometimes it’s not enough.  In my previous newsletters, I’ve mentioned the vast numbers of hydroelectric dams on our waterways – I neglected to mention the effect they’ve had on our native fish populations.

These days, nearly all of our dams have some sort of fish ladder or other passage installed to allow our native populations of fish to migrate upriver.  Remarkably, over the short time they’ve been installed, many of our native fish populations have already evolved to compensate for the different travel methods.  As it stands, we’ve had remarkable luck with reintroduction of species and hatchery programs, though I am by no means an expert on the matter.  Of course, like all programs, there have been hiccups.  For example, when the Clackamas River’s Cazadero Dam was constructed and put into service in 1907, a program began to trap the Chinook for hatchery brood stock was implemented and continued until 1939.  In 1922, however, the Cazadero fish ladder failed and cut off the upper and lower portions of the river, entirely halting fish migration, until the ladder was repaired in 1939.  The remnant populations from the lower river returned up the fish ladder and repopulated the upper reaches. 


Alternately, the Sandy River has seen quite a bit of trouble lately.  With construction on a new highway bridge over the mouth of the river, the flow has been changed and the mouth has been rerouted.  It would seem that the native fish aren’t fond of the relocation of the entrance to their home and runs have drastically decreased since construction began.  As if to add insult to injury, a tanker truck accident occurred two days ago in which the semi jack-knifed and spilled a quantity of hot asphalt down the embankment into the river.   While the tanker held 14 tons of the material, it’s not clear how much spilled and how much of the spillage made it into a river.  Thankfully, the Oregon Department of Environmental Quality is already working on the scene to clean up the spill and assess the damage.


While it seems as though our recovery methods are occasionally for naught or offset by accidents such as this tanker spill, we have good news in our area – within the past couple years, we’ve seen post-spawn adult Coho salmon in a local waterway, Johnson’s Creek which winds through our lovely city.  Successful spawns have officially been recorded, with dozens upon dozens of tiny fry occupying the little creek’s pools and shaded areas.

1024px-Johnson Creek2

Finally, I wanted to mention that we just picked up some new T-shirts, a joint venture with Repashy Foods.  They’re $15 apiece and available in S, M, L and XL in heather grey.


Well, thanks again, and next week we’ll be back to our typical newsletter format – Let me know if there’s anything you’d like to see!

Jessica Supalla