[34cygni]

Originally Posted by taricha

If you were to add a cryptic zone to the typical Display -> Algae Fuge / ATS -> Display. Where would you put it sequentially?

In terms of trying to dino-proof a system by pushing its microbiome towards coral dominance, the purpose of sponges is to serve as a sink for algal DOC and to filter algae-friendly bacterioplankton out of the water, so that suggests they should be downstream of the algae. And since sponges poop coral chow, that suggests they should be upstream of the corals. So it looks to me like it should be:

display tank ---> macro/ATS ---> cryptic biofilter ---> display tank

But that Tank of the Month implements a cryptic sump with an unusual split flow, and there are hobby blogs and threads describing systems with intriguing sump layouts and Calfo-style RDSBs and cryptic fuges and whatever else that might work just as well. I'm sure there are reefers out there who've been capturing the benefits of the sponge loop for years without ever having heard of it because they're good hobbyists and good observers and they go with what makes their livestock happy.

So let a thousand flowers bloom -- I have no wish to be the arbiter of how to correctly set up a cryptic biofilter. This is the closest I've come to speaking to that point...

Originally Posted by 34cygni

I've known for a while, now, that a coral reef is basically a vast algae scrubber sitting on top of an even bigger bacterial biofilter, and I've seen divers exploring reef caves on TV, but I had no idea there was a full-on cryptic zone underlying the entire reef structure! How cool is that?!? This suggests that the ideal setup for a hobby system would be a reef tank draining into a countercyclically lit display fuge with a Shimek-compliant DSB (...not necessarily in overall volume, but in terms of depth and the absence of counterindicated fauna so as to maintain benthic biodiversity -- at last, an excuse for the marine hobbyist to buy a hex tank!), which drains in turn into a large (ie, spanning the width of the stand for the two tanks above) cryptic sump with LR and a shallow sand bed where sponges consume labile DOC from the nutrient-limited macro and release POC for the corals.

...and in retrospect, I regret describing this as the "ideal setup". It might be my dreamquarium, no doubt in part because I've got a thirdhand 75 G acrylic hex standing empty, but it's only one possible implementation of the idea. Chalk it up to enthusiasm after discovering the sponge loop in the literature.

Sponges don't like microbubbles, BTW, and generally speaking, they do like Si. About 75% of sponge species have siliceous skeletons that don't readily dissolve and recycle if they die -- sponges can potentially live for centuries, perhaps thousands of years. Diatoms normally outcompete sponges for Si in the wild, but a "sponge scrubber" may give sponges enough of an unfair advantage to compete effectively. It would be interesting to try a cryptic biofilter in a system with a persistent diatom problem and see if the sponges can turn the tide.

Originally Posted by taricha

I still have my live sand, that I've pitched dinos into occasionally. What did you have in mind?

Seeding toxic algae blooms with algicidal bacteria is an accepted biological control measure, so I'm back to thinking about green algae disliking dinos and wondering if an algae-dominant tank is a source of dinocidal bacteria that can be cultivated with cellulose... The simplest approach would be to take water and sand samples and dose NatureMade B12 heavily in hopes that the cellulose in the pills will trigger visible bacteria blooms that could be tested against ostis (...stearic acid turns out to be rather interesting -- have you looked into fatty acids at all? -- but it appears to be consumed in the synthesis of bacteria cell walls, so while I'm concerned that some unwanted, non-cellulolytic bacteria will come along and eat it, maybe it's a good thing to have in the mix). Note that you may have to oxygenate if you get a bacteria bloom, as bacterial respiration will draw down dissolved oxygen and might crash the culture.

Another approach would be to dose your live sand tank with OTC B12 every day for a week, and every day take a sample of sand and put it in a beaker with osti-infested sand. A shift from the healthy live sand being taken over by ostis to live sand killing ostis might indicate the presence of dinocidal bacteria -- or it might indicate that your ciliates are all pumped up on B12 and ready for a fight. You might be able to tell the difference by looking for an increase in the ciliate population, as presumably the smaller the bump in ciliate numbers, the more dinos fell to bacteria, instead.

But maybe I'm fixated on green algae for no good reason. If the silica in Sundown Naturals B12 really did trigger the growth of diatoms, it's pretty impressive that they managed to rise up and defeat the ostis without any outside help. Dinos eat diatoms, and diatoms are presumably not okay with this, so they're probably friends with dinocidal bacteria, too. Maybe that's where to look for help -- after all, diatoms evolved after dinos, meaning they had to beat dinos so they could take their place in the sun. In the end, green algae lost that fight.

Originally Posted by taricha

you got me. I lol'd.

You're very kind to say so.