Fishless system?
 

This might sound like a stupid question but I can't remember ever seeing in asked or answered. If you have a system with no fish - only corals and clams - what would be the effects of this - so no fish - no feeding - no fish waste. Would you have to suppliment the system with an additive of some sort like Phyto for softies and some LPS. What about if you only have SPS? Are just regular water changes and maintaining good water quality enough for these corals to get what they need to grow and thrive?
I know I should probably be able to figure this out but have never had a system with no fish. The only inverts would probably be some snails although I may consider an anemone.

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No fish would mean less waste for sure. But there are other things in a reef tank that create waste.The very bacteria that break down the waste even produce their own, but since there would only be a minimal amount of waste being produced, a minimal population of bacteria would be present. I think the effect would mean less waste, but not eliminated. One would think that this would be a possitive thing, but I can't help but wonder if corals there is some kind of down fall?

I'll stop rambling now, too much coffee this morning.

Well that's the thing - I keep thinking there must be a downside - granted you water quality would probably be easy to maintain as you are not introducing waste into the system but.................... hmmmmmm

There are a couple fish that can offer positive effects like six line wrasses for instance because they eat some parasites on corals but for the most part no fish would mean a healthier system. When you have to feed fish you put food into the water that releases nutrients before even being eaten. Then the fish eat the food and eventually release waste into the water not only from the food but also from their own bodies. That is partly why some of the more experienced reefers with thriving tanks usually have very few fish in comparison. I've always wanted to leave a tank for a year without any fish to see just how much of a difference it would make but then one trip to the LFS seems to always foil that plan. I imagine a reef would establish itself way faster without any fish introduced to it as well; less nutrients, more pods, etc.

It's kind of unfortunate since part of the attraction of a natural reef is the unbelievable amount of activity because of the thousands of fish hovering about.

I had a fishless BB 37g monti cap tank for several months awhile back. It was great. No fish to feed, but there still seemed to seemed to be some crud accumulation, I suspect because there were probably hitchhiker crabs in the rock. I also had 2-3 snails in the system. IIRC, there was also a bit of film algae on the glass, so we still did weekly maintenance on the tank. For good coral growth, alk, Ca and Mg all have to be maintained, though I'm sure you're aware of that :)

Here's a pic:

http://www.lostmymarblz.com/37g-may-2005-2.jpg

I can't remember where I read it but I think it was on Anthony Calfo's forum on RF he stated that the corals actually use the fish waste as a food source....

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So the physical waste is benificial to the corals. But the by-product, namely disolved waste that breaks down into NO3 is not benifical. Interesting.

I think several researchers are now stating that corals actually get a fair percentage of their energy needs from food (as opposed to just light) so if you go fishless, feeding your corals would still be a good idea. SPS - maybe bbs or reefroids. Clams - phytoplankton. Corals with larger feeding tentacles usually need meatier fare, like mysis.

However, I would love to set up an experiment with identical lights & conditions & have one tank with feeding & the other without. Has anybody read any writeups on a similar expt?

Ruth, let us know what you end up doing & what are the results.

Anthony

Danny,

It may not be that NO3 is totally unbeneficial for corals, just that above a very low level it becomes harmful rather than helpful. In other words, the corals may use NO3 at low concentrations, but since the oceans are usually NO3 free since different organisms like macro algae & phytoplankton use it up, corals are not adapted to thrive in high NO3 environments. My softies, for instance, seem to do better when the water is not completely nutrient-free.

Anthony

What I may actually do is to go totally fishless for say 6 months or so - evaluate how things look, growth etc. and then perhaps introduce an anemone. The anemone would of course be fed and would presumably produce waste.
If I am not getting the results I may then just add say 3 or 5 firefish (it's a 100g system with probably an additional 25g in the sump). So far all that is in there are 1 lonely SPS , 2 Crocea clams that are smiling and happy and probably 25 or so snails. Calcium reactor will be hooked up this weekend so maintaining ca/alk/magnesium will be taken care of (I add mag. chips to my reactor which seems to work to keep my mag. levels about 1450) Should be interesting. I am going to continue to feed the tank with Phytofeast for the clams probably 2 times a week or so.