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jasalmanza
09/22/2006, 05:16 PM
I am currently sttingup a sump/fuge, and was thinking of running a "reverse daylight" cycle. I currently dose kalk at night to combat swings in pH boost growth, etc. So my question is when would be the best time to dose the kalk running this cycle?

Randy Holmes-Farley
09/22/2006, 05:25 PM
I dose limewater 24/7. When is best depends a bit on when your system pH is lowest. Most often, that is during main tank night, but if the refugium is big and bright enough, it may not be.

Here's a preview of some conclusions from next months Reefkeeping article on CO2 and photosynthesis that might impact your setup:

Implications for Reef Aquarium Husbandry
There are several things that aquarists can do to ensure the ready availability of carbon dioxide to photosynthetic marine organisms. While adequate studies have not been done with the exact species and exact conditions present in a reef aquarium to make definitive statements, the following principles may be prudent to follow in order to maximize photosynthesis:
1. Limit the pH maximum that is attained in reef aquaria. I’d suggest limiting the pH to no more than 8.5, and lower is better from a photosynthesis perspective (although pH below 8.2 has its own disadvantages related to rates of calcification by corals and coralline algae).
2. Put a lit refugium containing macroalgae on a reverse light cycle to the main tank. Not only will this limit the maximum pH attained in both the refugium and the main aquarium, but it keeps the pH lower in the refugium precisely when the organisms in it most need the pH to be lower (during the refugium light cycle when CO2 is required).
3. Do not drip limewater (kalkwasser) into or upstream of a lit macroalgae refugium, since it limits availability of CO2.
4. Do add the effluent of a CaCO3/CO2 reactor into or upstream of a lit macroalgae refugium, as it increases the availability of CO2.
5. The data on continuous light vs. day/night cycling is intriguing, and suggests that a dark cycle may be beneficial for lit macroalgae refugia, especially when the cost of the electricity to drive the lights is considered.
6. Keep the carbonate alkalinity up to at least 2.5 meq/l (7 dKH; 125 ppm calcium carbonate equivalents) to provide adequate bicarbonate for photosynthesis. Higher alkalinity may even be better, especially if the pH is also high, limiting carbon dioxide itself as a CO2 source for photosynthesizing organisms. This suggestion is likely already followed by most reef aquarists, but perhaps not by some with fish only or related types of aquaria that also rely on macroalgae for nutrient export.