Native marine aquaria are pretty scarce. Little information exists on how to be successful in maintaining healthy coldwater marine systems in domestic aquaria.

Hopefully this record of my failures, triumphs and ideas will assist others interested in keeping some of our fascinating, beautiful and often little known sea denizens in aquariums.

Sunday, 20 May 2012


Todays water temperature at Kimmeridge Bay is a rather cool 11.5C. How important is it to try to keep a native aquarium at a similar seasonal temperature to that found naturally? Most native reefkeepers will settle for an average mean stable temperature. I have usually aimed for 16C, but in the middle of summer this is both expensive and difficult to acheive.

My old chiller seemed to pack up a few months ago. The  reservoir seemed to require almost daily topping up and the unit seemed ineffective. So I found another chiller and yesterday I flushed it out and connected it up. Its a different model from the last one. Same manufacturer but instead of 2 coils it has at least 3 with an additional 'water in' and 'water out port' which seems to circulate reservoir water. Blowing through the 'water in' port didnt produce any flow from the 'water out' port indicating that 'water in' filled the reservoir. Perhaps chilled water served at point of use passed directly through the reservoir?
Anyway - I switched the unit on and began to fill the reservoir. When I reached about 2/3rds of the way to the overflow height the 'water out' port began to pump out. I connected it to the 'water in' port to recirculate it using 10mm Speedfit fittings.
The remaining 3 pairs I connected together to maximise contact time for the pumped aquarium water. The return water is markedly cooler than the tank temperature so its certainly chilling effectively.
However, the new unit has no thermostat. Obviously some form of temperature control needs to be installed and I settled for an STC 1000 at a cost of only £26. With the probe in the display tank - or maybe the 1st stage settlement tank I can use it to control the chiller.

Current aquarium temperature is 13.5C. Warmer than local sea temperature, but still uncomfortably cool when up to my armpit in the tank!

Late summer sea temperatures at Kimmeridge reach a balmy 18C. How practical it will prove to attempt to mimic natural fluctuations remains to be seen. I suspect it will prove too arduous a chore and I will settle again for a mean of about 16. However, it occurs to me that natural cycles are triggered by temperature (amongst other factors) and we should try to replicate this in some way.

edit: 21.05.12 Temperature now 12.3C. Chiller working very well indeed. I fitted the new controller, and its very easy to set, so with reminders I may be able to adjust it say 4 times a year to replicate local sea temperatures.
To suit native reefs a monthly temperature programme would be a rather useful upgrade.....


  1. What make of chiller please? I have broken mine (connections) at the moment and I am worried about leaks. I am having a break after thirty years. For redecorations and because of the electricity bill. I maintained a maximum of 22 degrees C in a 50 gallon aquarium. In breeding season this was lower.

  2. I think its a Cornelius - no badge unfortunately.