To skim or not to skim

[Osric]

I recently sent this to WWM and also wanted to gather thoughts and experience here. I've read http://www.wetwebmedia.com/toskimornotfaq.htm and can't quite put together the conclusive answer on skimmers.

 

I understand that they will remove dissolved organics, especially nutrients that nuisance algae might thrive upon, provide oxygenation and some pH buffer. If these points are incorrect please correct me.

 

Meanwhile, I have a 34 gallon system that is 16 months old (a Solana cube) lit by 150W metal halide with an upgraded Tunze return pump running a little over 600 gallons/hour and a Vortex MP20 on 100% reef crest random mode (that is, random flow between 500 and 2000 gallons per hour, hits maximums and minumums perhaps 2 times in a minute each). The center chamber is lit 24/7 with 18W of 6700 power compact lights and contains chaeto and chemi-pure elite; while the only skimmer the system has ever had is the stock skimmer, which at its best can pull out 1/2 cup of light brown skimmate a week.

 

Fish: 1 flame angel (I understand there is some debate about whether the tank size is sufficient for this fish); 2 ocellaris clownfish; and a lawnmower blenny. For the bulk of the year this system also contained a 6-line wrasse but I didn't do my research when I removed the top to control heat for the summer and he jumped.

 

Inverts: 1 cleaner shrimp, 1 purple-bodied boxer shrimp, 3 green BTAs (started as 1; original split more than a year ago and one of the children split again a few weeks ago), a small (4"?) maxima clam, and a coco worm. I am currently putting in about 1/2 a cup of live phytoplankton every other day with the filter feeders in mind.

 

Corals: 1 frogspawn, 1 largish galaxea, 1 starving sun coral, 1 trumpet coral, 1 acropora, a small colony of zoas, about 15 heads of ricordea, and a few (< 8) mushrooms.

 

Cleanup: 5-8 dwarf hermit crabs; 4-6 turbo snails.

 

Greenish/brown algae grows on the glass, and tiny filamentous brown algae thrives on some (but not all) rocks, especially where the rockwork shades the tank.

 

I couldn't say my chaeto is going crazy, but it's growing. The algae on the glass is hard to keep under control; I do not particularly know why, but snail fatality outpaces my desire to replace them. I have only recently added an ATO and wondered if salinity changes are to blame (ranging from 32ppt - 36ppt with poor topoff procedures; now with the ATO which I added only a few weeks ago it's trivial to keep salinity pegged at 35ppt).

 

Parameters are all 0 (ammonia, nitrite, nitrate, phosphate). Tank temperature from about 79 - 81 degrees. Water changes probably the biggest husbandry problem ranging from 10g/month on one extreme to 5g every other day on the other extreme (as in when I notice nitrate reading > 0, and I have seen it as high as 20 with no chaeto but at that time a skimmer running).

 

So my problem is I'd like to decide if my tank is really OK without a skimmer or not. Yet it seems impossible. If the skimmer's job is to remove organics that would otherwise materialize as non-zero phosphate or nitrate readings, I think there is enough algae growing in my tank to take up all the nitrate/phosphate and keep my readings at 0, telling me nothing about whether a skimmer would help or not. The clam and coco worm are fine now, but I imagine if I introduced a skimmer it would still be very difficult to tell if I was starving them for several months. I find the phytoplankton rather expensive, but am not clear if these animals will do well without it, especially in the presence of a skimmer (I am looking at a euro-reef nano system model, which seem to produce very dark skimmate and have to recommend them that the company wouldn't sell me a skimmer to fit my tank but insist it much protrude from this tank in order to function well).

 

So my specific question is: what specifically can I measure, at what intervals, in order to decide I require or do not require a skimmer?

 

And my follow up is, assuming those measurements show no need, what is the maximum number of days the tank can go with no maintenance (and no feeding either) before I will surely regret the lack of a skimmer or maintenance?

 

thanks in advance!

Osric

[jeremai]

Interesting. It sounds like your tank is running fine without a skimmer, as it stands right now. You have a pretty heavy bioload, especially with the phyto input, but it sounds like it's holding its own.

 

The only issue then is the waterchange schedule. If you changed, say, 5g/wk religiously, you'd be set. Since your schedule fluctuates so much, a skimmer could be a way to even things out, so to speak. Sort of a backup in case you go without waterchanges for a few weeks.

 

In the end though, there is no definitive answer. To skim or not is a highly variable question specific to each and every system.

[Amphiprion1]

If your tank is functioning satisfactorily without a skimmer, I see no reason to add one. Over the years, I've found myself paring more and more equipment out of the equation as far as my tanks go. The most high tech piece of equipment on my current tank is the fancy reflector for my halide. It is filtered just about entirely by macroalgae, turf scrubbing, and seagrasses. I say almost since the exception would be that I use carbon on a regular basis and it is changed frequently. Water changes are infrequent and not on a fixed schedule. Granted, I don't really have any sensitive corals and the display is mostly focused on seagrass, but the N and P levels are undetectable. I use large amounts of food in order to raise both N and P levels for good growth, but the actual concentrations never manifest in test kits.

[Freakin]

Presence of nuisance algae when you are running macro and doing WC indicates extra N&P IMO.

 

You could also consider dosing vodka/sugar/etc. that may allow your skimmer to do the work you require of it.