Hi Folks,
I have put my skimmer back for the reasons below.
1. My 70G tank seems to be too small for an organic cycle to happen (or I keep too many fish)
I really liked the idea of organic cycle where excess nutrients are naturally processed by abundant bacteria. From what I see from the comments of so many skimmerless people here, I'm pretty certain skimmerless is possible, there's almost no doubt about it to me. But with all the eight fish I keep in the closed environment, NO3 indicated that the bio load of my tank could exceed the naturally sustainable level.
Like I wrote, I have once achieved all zero readings, but after I replaced my test kits to brand new ones, NO3 was 5, but the color chart was really hard to read, and it was very 10ish 5. So I now doubt my previous test kits could have been too old and inaccurate. Even if my previous ones were valid, the fact is that I have a very 10ish 5 NO3 right now.
2. Functionality diversification
As Randy puts, I now believe skimmers and chaeto have different functions. In my case, after taking the skimmer off, NO3 kept rising while PO4 was zero, which means chaeto is extremely good at consuming PO4, but not as good as a skimmer in terms of NO3 reduction. I think in order to have major parameters, such as NH3/NH4, NO2, NO3, and PO4, in check, letting a skimmer do its job is one way. I don't say it's the best way, but an easy and safe way.
3. pH safety net
Actually, my pH has been 7.8 in the morning and 8.2 during the day and evening, and my pH levels haven't caused any trouble by now. My chaeto was lit 24H and I even stirred water surface of the sump using a pump. So this might not have been an issue for me. But, just as an additional backup to keep pH in a right range, skimmer may be good. I'm not saying you must have a skimmer, but I would say safer. Needles to say, a skimmer doesn't have any ill effect. So there's nothing wrong having one in my sump. In the Randy's article below, I found some facts I can't ignore.
http://www.reefkeeping.com/issues/2004-09/rhf/
In a sense, all that most aquarists need to know is that pH is a measure of the hydrogen ions in solution, and that the scale is logarithmic. That is, at pH 6 there is 10 times as much H+ as at pH 7, and that at pH 6 there is 100 times as much H+ as at pH 8. Consequently, a small change in pH can mean a big change in the concentration of H+ in the water.
This means though the swing of pH looks tiny for a keeper like me, the swing could be huge for those sea water creatures. They should be able to tolerate some swing to some extent, but I want my tank to be better, not just tolerable.
4. Heavy feeding
I could have reduced my feeding and wait for the NO3 level slowly subsides, and this is a very realistic option for some people, I believe. But my tank mates are aggressive eaters, especially my margined coral fish loves raw or frozen cram and other meaty foods, and I don't want to impose a food restriction on him. Fat fish looks nice and beautiful.
Some thoughts
Surface of my live rocks became noticeably cleaner after taking off my skimmer, which suggests if I kept skimmerless, my tank could have been cleaner. Does it mean biological filtration became active by stopping the mechanical filtration?
I still like some aspects of not having a skimmer; less heat source, no noise, no electricity, more space in the sump, etc. My previous skimmer pump was suddenly dead and it was really chaotic. I had hard time finding a right one in a very short period of time, but the skimmer pump of the one I got was defective and I had to ask the manufacturer to replace it. If bio filter provides a complete cycle, then there's no need to worry about such confusion.
Again, depending on your bio load, skimmerless could even be a favorable option for the reasons mentioned above, and it's the matter of choice, not about which is better. Also, even though my chaeto amount is big, what if the amount is doubled? It could effectively put all params in check, maybe. I actually like this kind of challenge, but I can't risk my tank mates for my curiosity.
Maybe there should be two different categories, light bio load skimmerless and heavy bio load skimmerless. My tank is somehwhere in between, meaning there involves some risks.
In my mind, there is no conclusion on this. And I believe I don't have to conclude on it. I just took a safer path at this time, and there's nothing wrong with it. And there's absolutely nothing wrong for those who do skimmerless, of course. I would like to thank all you guys who commented here. I think I leaned a lot. All comments were very helpful to me. Thank you!
