| Russter |
01/08/2011 12:18 PM |
Just thought I would add this from another thread seeing as no one answered in this one.
[QUOTE=mr.wilson;18154582]I get a lot of PMs asking me to expand on some of the topics that I briefly touch on in this thread. I enjoy answering them and find it to be a useful way of establishing where interest lies and what people would like to see in a book. I have had a few people ask about shutting things off at night (specifically the protein skimmer) so here is a general response to the topic. I prefer to post it here where everyone can share their ideas and information. It's hard to tell where to begin and where to end with a topic within the scope of the thread, as everything is interrelated. I didn't talk about reducing the flow rate in the display at night, but if I ramble on too long I will lose most of you. Even my attention span drops off at my own musings :)
The skimmer takes out carbon (toc) and bacteria. Both of these are food sources for corals and fish. Many skimmerless tanks have better polyp extension and growth rates. The problem is, these tanks can also have yellow water, turbidity (cloudiness) and nuisance algae problems. I have even had phytoplankton blooms (green water) in skimmerless reef tanks. Until we find a better way, a compromise between a natural and mechanical system is the safe route. Shutting the skimmer off half of the time is a good place to start. If conditions get better or worse, you know which direction to go; if they stay the same, it still confirms the limitation of protein skimming. Then you start to think if it was really worth it to upgrade your skimmer the last two times :) I don't see a benefit in any schedule other than 12 hrs on, 12 hrs off.
So now that we have decided how long to shut it down for (12 hrs/day), we need to decide on the best time. The fish and corals are most active during the day during photosynthesis, and at night the corals open their feeding tentacles to collect the plankton that come out when the lights go out. Shutting the skimmer off at night seems to be the smart move, and if it influences the flow in the tank to slow down, even better.
One way of achieving the shut down is to have the pump on a timer. This is the quick and easy way, but the preferred method is a VFD to slow down the pump to allow the skimmer to "simmer" so it can still function if there is a spawning event or call for skimming. A VFD also allows you to ramp up to wet skimming a few times a day to keep the skimmer neck clean, grab some stubborn (semi-hydrophobic proteins), and do a passive water change (just keep an eye on salinity).
Pumps with flow control are expensive. You may be able to set up a cheaper solenoid that restricts the air line feeding the needle wheel. You will have to get creative and rig it to shut only part way at night so some air can still bleed in. Drilling a hole in the solenoid may work, but I'm not sure how you will "tune" it. Skimmers with two or more needle wheel pumps make it easy because you just need to keep one pump on and put the rest of them to sleep at night.
At this point in time you are probably asking yourself, "Then why not just turn down the skimmer and run it 24/7?"... or even, "Why not use an undersized or cheapo skimmer and put the money elsewhere in the system?". The key here is having skimmer reliability, and you simply won't get that with the cheapo skimmers on the market. When they go "on strike" or flood the collection cup, when the air intake crystallizes, or the water level varies, or the pump disconnects, or stops entirely, you don't have a skimmer, and you can't predict when this will happen. With a well designed skimmer, you buy peace of mind and in the long run, you pay less because you buy just one skimmer. In other words, do it right the first time, and do it once. The other option of running a premium skimmer on a slow and steady, conservative setting is a "neither here nor there" solution. You end up with the worst of both worlds because the skimmer neck will slow down efficiency with skimmate (muck) build-up in the neck, which you will have to clean manually. It also doesn't achieve our goal of leaving the tank "natural" during the nightly plankton swim.
Shutting ozone down at night is a parallel issue. You can put your ozonizer on the same timer as your needle wheel pump. Your ORP controller may have a day and night setting. UV sterilizers may be worth shutting down at night as well, but don't start unplugging everything at once; ease into a night mode one device at a time over a few weeks. This way there is no shock to the system and you will have a better handle on the repercussions of each device.
While we are on the subject, there may be merit in shutting the refugium off during its night/dark phase. During the "day" algae utilizes/removes nutrients (nitrate, phosphate, heavy metals etc.) during photosynthesis (cellular respiration). The algae in your refugium converts "bad" Co2 into "good" o2; however, during the "night" (photorespiration) algae converts o2 into Co2 thus lowering the PH (liquid Co2 is carbonic acid, and like any acid it lowers PH). The same PH shift and gas exchange occurs within your corals carried out by symbiotic algae (zooxanthellae). Many people run their refugium on a reverse photo-period (refugium illuminated at night and kept dark during the day) to balance the PH and photosynthetic processes of the refugium and display. During the day, the zooxanthellae are generating o2 for the refugium while consuming the Co2 the refugium is producing, and the reverse process at night. At night the algae in the refugium leaks out some of its nutrient catch. If you take the refugium off-line during its night/dark phase, it assures that the leaked nutrients don't make it to the display tank. When the lights come back on over the refugium (which should have 16 hrs of light and 8 hrs of darkness) the algae will re-absorb the lost nutrients.
Thanks Mr. Wilson!
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