There is very little practical information out there on keeping a cold water reef. Most public systems are open water and not very relevant. When I go diving in Puget Sound, there is just so much colorful and interesting life..... I wanted to see how a cold system..beyond the usual tidepool/lobster tank...could function with our current warm water reef techniques. I've had this system set up for about 18 months now. Originally, these two tanks were set up with no aesthetic vision in mind. If this were a real display..the tanks would be much better presented....without the visual pollution of lights, plumbing, and equipment.....and....with much more attention paid to aquascaping and aesthetic maintenance. So far this is what I've discovered....
1) these tanks are much easier and less costly to run that a similar sized sps reef since lightning, flow, Ca additions, etc are all less or not necessary in a cold system. Yes....there's a chiller.....and a good skimmer is a good idea...but, that's it for equipment.
2) Because everything....or most things..... are non photosynthetic, you must feed quite a bit....much more than we feed in a warm reef. This extra feeding will lead to a lowering water quality. A good skimmer helps here....but, I've also been using oysters. When I dive....I notice that the water's visabilty dramatically improves over the oyster beds.....so, I placed a few in to see how they would fair. After about a year without losing my couple of oysters, I placed about 50 in the system. Since their addition, the tank's water has seen less
algae growth, improved clarity, while the skimmer produces less.......and.....they look great since they fuse together and make great aquascaping rocks.
3) fish disease is much less prevelent than warm water. I did lose a fish to a type of rapid fungas early on....but, that's it.
4) Cold tanks tend to run at a low pH from their being no photosynthetic activity. These tanks also have minimal evaporation......the total system (about 150gal of water) evaporates less than 1 liter a day. To help keep the pH up, I wanted to increase evaporation so that I could top off with kalk. With the aid of sump fans, I got the evaporation up to about 3 liters a day. I pull kalk from my warm water
kalk reactor to top off the cold system......with this kalk addition, the cold tank's pH stays around 8.3 24/7......up from 7.8.
5) I've been able to keep critters that challenge warm water keepers....like oysters, mussels, and crinoids.....yes crinoids....aka feather star. My golden crinoid has been with me for over a year now and has grown. I do not directly feed it. There are some soft dendro like soft corals as well as gorgonians available in Puget Sound that I want to try next. In our warm water tanks, we are so preoccupied with minimizing food imports....in a cold tank.....mass food additions are part of the game.....so maybe that's why some things that normally don't do well are doing great in the cold system.
6) tank sweating is an issue. My tanks and sump were made from 1" thick acrylic and haven't sweated a drop with a tank temp of 55 F....but, I have seen a few other cold reefs that were using 3/8" acrylic.....and they sweated. Glass really isn't a good option since it will sweat at any thickness.
7) as for feeding....I've been feeding meaty seafods like scallop.....oyster eggs, rotifers, some phyto, and I always bring back some live plankton when I dive.
Bob Morse
