6 gallon SPS pico reef pushes the boundaries for nano tank enthusiasts

SPS corals are known for their higher level of care and sometimes difficult nature as far as corals go – most SPS aquarium set ups include high flow, high light, and big aquariums teeming with other invertebrate and fish life. With the increase in nano reef tanks in recent years, we’ve been seeing a lot more examples of simplified mini versions of the former.

Many of them end up looking just as beautiful and this tiny pico tank by Singaporean fish breeder JunKai who bred the oblique dottyback is no exception. At only slightly more than 5 gallons, balancing the water chemistry to suit the needs of the coral inhabitants is not so simple.

The 60cm x 23cm x 20cm pico tank is equipped with 2 units of Par 38 Cree spotlights.

The nano SPS reef was inspired by Marcello’s tiny reef garden and features a 60x23x20 cm tank equipped with two units of 12K Par 32 Cree LED spotlights. The set up is barebottom, skimmer-less, wavemaker-less and devoid of almost all familiar aquarium related equipment except for a 600L/Hr hang on filter and until recently, a dosing pump for administration of calcium and other additives. The volume of the tank roughly equates to 7 gallons, but taking into account the few pieces of liverocks, the total effective water volume of the tank is just about 6 gallons.

A small pink Stylophora growing next to an encrusting Montipora. The Montipora showed very good growth and you can see the original frag as well as the large portion in which it grew out from.

A small group of Aioliops megastigma. These didn’t last very long as they were spooked easily which resulted in jumping related casualties due to the shallow tank. They were re-homed eventually.

The main livestock housed in this tank includes various species of SPS corals, a few shrimps mainly in the Urocaridella and Leander genera, some nano gobies including Aioliops megastigma, Elacatinus multifasciatus, Stonogobiops xanthorhinica, a pair of Discordipinna griessingeri and other nano gobies. The tank also had a half inch african flameback angelfish which was cute for awhile, but as it grew bigger, it had to be relocated.

Being a very tiny and shallow tank, some of the fish, especially the A. megastigma, got spooked easily whenever the lights turned on and off, and therefore jump out of the tank easily. The tiny gobies that were prone to jumping were relocated and the pico tank mainly featured SPS and invertebrates. The fish now only consists of one or two Eviota gobies and a pair of Priolepis nocturna. Due to the small water volume and the lack of a protein skimmer, water changes of two liters were performed once every day or once every two days. The hang on filter also included biohome and zeolites for biological filtration.

The blue staghorn shown here was when it was first glued to the rockscape.

The same staghorn as above a few months later.

Apart from the diligent water changes, daily siphoning of detritus was also carried out. You’ll be surprised how much detritus can accumulate from what little liverock and feeding that is in the tank. The only flow provided for the SPS comes from the hang on filter, and as a result, not everywhere in the tank is suitable for SPS growth. During the first few months of maintenance, Two Little Fishies part A and part B Calcium and Alkalinity two part additives were manually supplemented, but as the growth of the SPS increased, a dosing pump was used to keep up with the supplementation of calcium.

Evaporation is not as high as you’d imagine and the tank is placed in a windy location of the house. The small water volume meant that a cool breeze is all that is needed to keep the tank cool at 27-28 degrees Celsius. Despite the unbelievably simple set up, the SPS corals thrive in this tank as can be seen in the following pictures.

The growth of the Montipora showing before and after shots. The aggressive and rampant growth of this Montipora is actually quite damaging to nearby corals so much so that it is considered a pest.

As can be seen below, all the corals that are in the tank started out as small frags that eventually grew out. The corals predominantly consists of Seriatopora, but also include other Acropora, Stylopora and Montipora species.

The tank seen here in its early days where all the coral were still small frags.

It doesn’t take too long before they all grow into mini colonies. The SPS corals are heavily fragged each time they grow too “big”.

The tank has been running for about two years now and most of the SPS that are growing in this tank has been there since day one. Having seen this tank multiple times in person, it never fails to impress me how the simplicity of this tank can manage to upkeep so many SPS and even two crocea clams. The clams have grown at least an inch since, in the year or so that it has been in this system.

The colors aren’t quite as nice as they could have been in stronger lights though, but dying they most certainly are not. Due to the really small space for growth, the SPS are subjected to regular pruning to ensure they do not get too “big” for the tiny tank. Since all the SPS grow at different rates and need to be pruned at different times, there’s rarely a time frame where all the corals are nice and big to take a good enough full tank picture. Here’s a picture of JunKai’s pico SPS tank just after a round of pruning. Within a few months the SPS will bounce back bushier as before.

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KaiTheFishGuy

Kai is a systematic ichthyologist at The Australian Museum, Sydney. His research interests combine the use of cutting-edge next generation sequencing techniques with traditional methods of morphology to better understand the evolutionary history of coral reef fishes. He is a legacy ReefBuilders contributor, having previously written close to give hundred articles under his pseudonym LemonTYK.