The Digital-Reefs Black Tank – Stocking Begins

Well, so much has happened since our last update that it’s hard to know where to start. Actually, if we don’t sit down and take a few moments we’ll probably have even more to add…. so let’s just get cracking! In our last installment, the tank had recently been inoculated with live rock and we’d observed as nutrient levels had stabilised generally. In essence the tank was ‘born’ and we were now custodians of a fully functioning miniature reef ecosystem.

Since that update, we’ve been busy managing the development of the display and the first part of this was to get the major disruption of finalising the aquascape done and dusted. As such we removed some of the live rock we’d been sent and reduced the amount in tank to about 35kg. This allowed us to build a rather more minimal structure but still allowed for a decent cave system which we feel is critical to providing a refuge for the fishes in the tank, for providing a variety of microhabitats, and for making the tank visually interesting close-up. With plenty of negative space, even allowing for eventual coral growth, we devised a twin-bommie layout, with one side proportionately larger than the other and a branch rock ‘bridge’ forming a natural archway between the two. During the creation of this aquascape compositional techniques (such as the ‘rule of thirds’ and ‘golden section’) were considered, but we also went a step beyond this and envisaged how coral growth would impact on the scene. As a result, please note that the aquascape should be come more balanced as the system matures. Of course, we also had to compose the aquascape to look aesthetically pleasing from both sides (as this is a room divider tank), and this proved to be extremely challenging! It was so difficult that we couldn’t secure the structure other than to make sure it was all stacked solidly. We hope this doesn’t come back to haunt us in the future but really, there’s no way we’d have been able to get the structure we wanted using putty, rods etc. Maybe if we had been using dry rock and we’d had enough space to view our work area from both sides it could have been done… but not in our situation.

Anyway, we were very pleased with the eventual structure and after several days without noticeable nutrient spikes or structural shifts we went ahead and started transferring stock over from the old tank. Using a fish trap, our juvenile Yellow Tang was first across and took to the new tank like… well ‘a fish to water’. With the tang settled and grazing on the odd patch of hair algae after just a couple of days, we then managed to capture the mature Starck’s Damsel and moved it across.

We’d have liked to have added this fish last out of the existing stock, but we couldn’t catch the other fish in the still full, old display. A few days later though, we had a window of opportunity to break-down the old tank completely and, after transferring selected corals over to the new tank, and packaging the rest (including the old live rock) for transport to a local fish store, we caught the Percula Clown and moved her across too. As suspected, the Starck’s Damsel gave her a hard time for a few hours but eventually things settled down. A disappointing thing occurred also… the Green Clown Goby that we’d had in the old tank disappeared during the breakdown (we saw it as we were removing some of the corals). All we can think is that it stowed away in some rockwork or coral and is now resident in the LFS where we took the other stuff! They are looking out for it and who knows, maybe it’ll show up. We were pretty gutted though as we’d had that fish for several years. Other residents of the old tank that we decided to keep included a tiger pistol shrimp that we’d all but forgotten about. Also we found our Edible Sea Cucumber who had gone missing several months earlier, now looking considerably smaller than when we last saw it. Clearly it wasn’t getting enough food in the old system so we’ve now moved it to the middle sump section where a thin layer of detritus seems to settle gradually and where we’ll continue to monitor it. The Pistol Shrimp was put into a floating breeding trap in the sump, with a length of pipework to hide in, for the time being (as we hadn’t added the substrate to the display yet).

Talking of the sump, we made a few further tweaks here and there to keep things running smoothly. Firstly, we altered the angle of the fan so that it was blowing straight down on the water surface in an attempt to enhance evaporative cooling. Over the Christmas holiday the house became quite warm on a number of occasions due to central heating/weather combination and, although controlled by the STC1000, the temperature did rise more than we’d have liked. We’ve since found that having the sump doors closed might cause the air inside to become so humid that evaporation ceases. As such, we are using the push-click stoppers on the cabinet to keep the doors slightly ajar overnight, and sometimes in the day, as this allows air to vent the cabinet at the top. We may also add a PC fan on the original vent hole at the wall end to pump air from the room into the cabinet, but as it is, the new trick seems to be working. Due to the 0.3 degree Celsius switching margin in the STC1000 the tank does normally fluctuate by around 1 deg C in a normal 24hrs. We were getting better accuracy than this with just a heater stat in the old system to be honest, but of course we don’t have the worry of a rogue heater sticking-on any more. Anyway, we are still using the digital thermometer with alarm from the old system as we can see this at a glance from the room too.

There have also been developments with the lighting on the system indeed we’ve now got our dimming cycle working well (we just kept the settings from the old tank actually). Basically our royal blue LED array (Channel 1) comes on at 0700, when this reaches 50% intensity at 0800, a purple and a blue tube come on (Channel 2). At 0900, the blue LEDs (CH1) are at 100% and the two tubes (CH2) are at 50%. At this point, the remaining 4 T5s (currently 2 blue, 2 50/50) start to ramp up (Channel 3). At 1000, the blue LEDs and 2 T5s are at 100% and the remaining 4 T5s are at 50%. Now, the white LEDs (CH4) start to ramp up. At 1100, everything is at 100% apart from the white LEDs which will take another hour to reach full intensity. This stays the same until 1800hrs and then channels start to fall-off in a reverse process. There’s a 20% chance of light dimming briefly down to about 80% intensity from the cloud programme. Originally running with 2 blues, we have added an ATI Purple tube into the mix recently, so we now have 1 ATI purple, 3 Arcadia blues and 2 Arcadia Marine Hybrid 50/50s. Overall we are pretty happy with this, but we may add an ATI Blue Plus tube and go down to just one 50/50. In the sump we are also using Arcadia lighting, but this time it’s an EcoAqua 30watt 5200k LED spotlight. As suspected, this is producing excellent growth from our Chaetomorpha and we think it has been instrumental in keeping nutrient levels reasonably low. Running on a reverse cycle to the main light (OK with a little overlap) we’ll continue to run it until our Chaeto becomes redundant (a possibility in the future given technologies we are planning to phase in).

Moving on to developments that have taken place in the last couple of weeks or so, we’ve replaced one of our original stream pumps with a much more powerful Tunze 6105. Running off a 7092 controller and fitted with wide-flow nozzle, we’ve now got this producing a mesmerising wave effect in the tank and its certainly seeming to suit the additional corals and fish we’ve added! Yes, the tank is young but we’ve added 6 gorgeous, premium SPS colonies and so far things are looking good. We’ve also added a couple of new fish to keep the YT, damsel and clownfish company… specifically a Flame Angel and a Scarlet Hawkfish. Two weeks on and both are now settled and feeding on flake and frozen. The Flame Angel came to us with one of its pelvic fins almost entirely gone but this is now growing back quickly. Again, the damsel acted territorially, this time for a few days, towards the Flame (it pretty much ignored the hawkfish) but things now seem to have settled. We may consider trapping the damsel in the future depending on what fish we decide to add. We are planning another large fast moving specimen, maybe another tang for the system plus some smaller fishes like gobies, maybe a dottyback, a couple of Halichoeres wrasse… a lot depends on what we can source, and when, though. Adding substrate to the tank was the done just a couple of days ago and we’ll have a more detailed review on this shortly.

So that brings us up to date, and begs a couple of tank shots. Please bear in mind that the system is still only very young and so coral cover is minimal at present. In the coming weeks we’ll be testing new water movement devices, adding Carbon and GFO reactors, connecting-up our Ph-controller and CO2 reactor.. and hopefully adding more livestock!


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