Up until now, I emptied the skim trap about once a week, or three times every two weeks. There would be about half an inch to three quarters of an inch of skim.
Now I'm seeing that much collected within an 18 hour period. I've been dumping it daily for the past few days. In the past, I've never seen the bubbles filling the trap. They've always just remained at the top. Now I have bubbles filling the trap except, of course, where the skim takes over.
So I wonder what's happening here? Could 10 less-than-one-inch crabs be increasing the detritus in the water column by an estimated factor of 10? Six Damsels occupy the tank. I don't quite think the crabs equate to 54 more Damsels (which would produce nutrients by that same factor of 10).
Already having 35 pounds of live rock, I, in essence, added an additional 43% of live rock. Does that translate into adding an additional 43% of nitrifying bacteria to the tank? Maybe not, but it's not a horrible estimate. With ammonia and nitrite readings effectively at zero for the past 4 to 5 weeks, I've potentially added 43% more bacteria without increasing their food source (ammonia and nitrites). Is this potential ammonia- and nitrite-starvation causing the nitrifying bacteria to reduce in population to a more sustainable number? Seems sound to me, but I'm no rocket surgeon.
I think the solution lies with both the large percentage of live rock added AND the crabs, with just a sprinkle of "lack of flow":
Sure, I added some animals to the tank along with the new live rock, but not enough to increase the amount of ammonia in the tank by my estimated 43%, which would be enough to feed the addition of 43% more nitifying bacteria. So some of these bacteria must be starving and dying off.
Without a powerhead (as of yet), the most flow that my live rocks and substrate gets is a very light flow from the power filter, which only effects the half of the tank the power filter is in. So there is a bit of "marine snow" sitting on my rock and substrate.
Watching the crabs, they tend to sift through this "snow" while grazing upon the substrate and rock. The first day they were introduced into the tank I noticed them tossing up a decent amount of white particulates. These particulates are particles that are decomposing and contributing to nutrient production.
My logic (whether false or not) is leading me to believe that the crabs are causing the increase in skimmage, not due to their bio-load in the tank, but by their behavior of tossing "snow". Remember, I have yet to introduce any flow to speak of to the tank so the live rock is not able to "clean" itself. To compound the issue, I've added an approximate 43% of nitrifying bacteria without an equivalent increase in their food supply. I believe the dead bacteria now contributes to part of my detritus.
This leads me to believe that I can expect another increase in skim production once flow is introduced into the tank. Flow will, in essence, be performing the same function as the crabs seem to... dusting off substrate and rock. If my logic is sound, skim production will increase, but also will not last as long as the crab-induced skim production will.
Prior to the introduction of the crabs, I was more than likely "under-skimming" - more "dead organic compounds" were being introduced into the system than were going through the skimmer.
Now that the crabs are sifting through protein particles while grazing, I have a little catch-up to do. More (hopefully, anyway) DOCs are making to the skimmer than are being created.
With the addition of flow in the next couple weeks, I feel confident that more nutrients will be skimmed than generated, allowing me to get caught up and then begin to find a new "normal" with the skim trap.
So now that I'm at the end of my thought process, the title of this entry seems misleading.
Comments? Alternate theories?
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