What is the smallest pico aquarium size ?

In recent years reef tanks have been getting smaller and smaller and a category that has exploded in popularity are pico tanks.  Generally speaking, any tank less than about 8 gallons would be considered a pico tank.  While some manufacturers offer tanks as small as 1 gallon, in reality, the smallest sized pico tank that is maintainable for the long term is a 5 or 6 gallon tank, such as the Reef Casa Flat 6.  While tiny pico tanks may make for an interesting short term project for experienced reefers, hobbyists of all experience levels will find them very difficult to maintain long term due to fluctuating water parameters, maintenance difficulties and very limited stocking options.

In any reef tank, a larger water volume provides a larger margin for error and helps to mitigate parameter swings.  Any mistakes in salinity, temperature, dosing etc. will have a smaller impact on a larger tank and allow  the hobbyist to notice and correct mistakes.  In a tank of less than 5 or 6 gallons, any errors or oversights will be magnified and can lead to a tank crash very quickly.

It also may seem counterintuitive, but keeping a tiny pico tank free of nuisance algae, cyanobacteria and other issues is actually far more difficult than in a larger tank.  Because nutrient levels can rise quite quickly in 2 or 3 gallon tanks (and then fall just as quickly with a water change) various nuisance organisms are able to take hold.  It is also very difficult to provide enough flow to prevent dead spots from forming as well, due to lack of available open space around the rockwork.  Detritus will inevitably collect in these dead spots, contributing to various types of algae.  Even cleaning the glass of a tiny pico tank can be quite difficult, since even the smallest nano scraper will likely not have enough room to fit around the rockwork.

The last reason why the minimum size for a long term pico tank is 5 or 6 gallons is the limited stocking options in a smaller tank.  Since corals do not have an off switch, a tiny pico tank will quickly become overgrown with corals, further complicating maintenance and impeding water flow.  It is also almost impossible to keep even the smallest fish long term in a tank less than 5 gallons.

While smaller tanks make a great choice for many hobbyists, there is such a thing as a tank that is too small.  Here at Reef Casa we want everyone to experience reefing success so we have designed the Flat 6 to hit that sweet spot between being small enough to set up almost anywhere, while still being large enough to set aquarists up for long term success.