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View Full Version : How a CUC REALLY works...and it's probably not what you think.


Sk8r
06/15/2012, 10:52 AM
A Cleanup Crew [CUC] is the next step after cycling. There's a lot of myth, a lot of angst about hair algae and 'getting something to eat it.' ***eddaboutit...re the 'eating' thing.

Your CUC will eat algae. So will copepods and many desirable creatures in your tank.

But they won't strip your tank of algae. They can't. Not remotely. Algae grows because your rock and sand have some phosphate (algae fuel) and they're starting to release that phosphate into the water. If you didn't use ro/di water in setup, you may really have a lot of phosphate. If you didn't wash your sand, yep, even more. So---how to get rid of the phosphate? Not a CUC. Either a refugium (an algae-farm) or a phosphate reactor (about 50.00 and highly effective, over about 3-4 months: do NOT expect instant results. Also DO NOT OVERDO: you need some algae for health and food for some species. Blennies need it; copepods need it; and your snails need it.)

SO---if they're not there to eat up all the algae, what ARE they there for?

One real reason, besides being cute: they poo. They poo gentle, usually non-high-protein veggie-based stuff into your baby sandbed, which right now has never handled high-volume fish poo. Over about a month (time for you to safely quarantine your first fish) they will slowly bring that baby, weakling sandbed up to strength enough to handle a fish's greater, more protein-based output. And believe me---fish can poo. A lot.

Once your tank matures and you have waste floating around, your CUC is still important: it re-poos the poo in micro-size that can slip down through the sand to get to the bacteria, who process it into nitrogen gas, which floats up as occasional bubble: that's why reefs don't use filters---their sandbeds break it all down. Fish-onlies may need a little more cleanup, and may need filters, because they're a bit more bare-bones and their sandbeds usually can't keep up. Not saying they couldn't with backup sandbeds, but they often don't.

What should be in your CUC? In the first month, I recommend cerith snails and strombus grazer snails; and scarlet hermits, which are wellbehaved. Don't get margaritas (coldwater, and soon die: they shouldn't even be sold) and don't get astraeas---they can't go on sand, fall over, starve, and crabs eat them, of course, after they're dead. Also you need bristleworms. If you also have other creatures from your live rock, generally, good: the more the merrier. Most worms are good; most volunteer crabs aren't. Shrimp---don't get shrimp right off. They have nothing to eat yet, anyway. [Coral bandeds can nip fish, or even kill them. ] Avoid nassarius and conches for the first 3 months. After your tank matures a bit, you can add 2 nassarius or 1 conch per 50 gallons of tank: you'll rarely see them, since they live under the sand and keep it clean for you---but they'll starve in a new tank.

Do not clean your sandbed: let the nassarius and conches do that---they don't disturb it as they work very small areas at a time---24/7/365.

Give your initial inverts a month in your newly-cycled tank and spend your spare time quarantining a fish and getting your water chemistry balanced: that's quite enough for a novice to do all at once. And that water chemistry is EVERYTHING.
I have good params for an lps reef in my sig line. Even if you're fish-only or softie coral, match those via water changes, (stony reefs ultimately need alk-cal-mg additives) and test for alkalinity obsessively. A log book is a good thing: don't trust your memory. If you've got a good CUC before you start bringing fish into the picture, you'll have less nitrate problems---if you have a sump and skimmer and fuge, probably NO nitrate problems. And if you are a fish-only, and your fish will eat a CUC, consider a refugium with CUC AND rock and sandbed: it'll make your life easier, giving you the advantage of an additional sandbed and rock to process waste, and a CUC your fish can't get at: if you have herbivores, you can also grow weed that your fish can't get at until you give it to them.

HTH you understand how CUC and sandbeds work.

tatorswife
06/15/2012, 10:59 AM
awesome post..That was just what we needed..You are so helpful :)

Mrs. Music
06/15/2012, 12:01 PM
SK8r. Very nice post. I always enjoy your posts and learn something too.

gnasher
06/15/2012, 12:17 PM
I'm curious, why do you differentiate between a FOWLR sandbed and that of a reef tank in terms of filtration?

mlott132
06/15/2012, 12:51 PM
Great post!

Mussin
06/15/2012, 12:56 PM
Im always tempted to vacc my sand bed during a water change (habit of the freshwater days) But I read one of your old post saying never to touch.

Jeremy

sponger0
06/15/2012, 01:06 PM
Awesome. I learned alot here. But people also want to keep in mind that a fuge is only effective if it is proportionally sized to the display tank.

Sk8r
06/15/2012, 01:17 PM
True, Sponger.
Re the question about the FOWLR sandbed, it's 3 things that set it apart. 1) Fish are usually larger and more numerous than you put in a reef. 2) they include fish who may eat a CUC, thus meaning that not only does poo not get pre-broken-down and sifted into the sandbed, it may be carnivore-poo, which is pretty strong stuff 3) they often don't have enough sand and rock to handle their fish-load even if it were pre-digested, relying instead on filters. As long as a filter is in the system the up and down of food supply (as the thing is cleaned then gets dirty) tends to keep the sandbed fluctuating in strength, as it doesn't get all the food it would get---[but would be overwhelmed if it got it all: the narrow band of 'just right' is not easy to hit.]

This is not saying you can't have a filterless reeflike FOWLR: but they're not as common as FOWLRs with a filter-assist.

Nipels
06/15/2012, 01:36 PM
How deep should a sand bed be for a 90 gallon Community tank with soft corals and reef fish?

sponger0
06/15/2012, 01:43 PM
How deep should a sand bed be for a 90 gallon Community tank with soft corals and reef fish?

IMO I think thats more of a personal preference. I like the critter that live in the sand so I give a deeper sand bed but 2" should be more than enough. My recent tank is about 3 and the next one I make will be 4 inches+

Reefer Ronnie
06/15/2012, 02:19 PM
Great post!

G x 2
06/15/2012, 02:59 PM
But they won't strip your tank of algae. They can't. Not remotely. Algae grows because your rock and sand have some phosphate (algae fuel) and they're starting to release that phosphate into the water. If you didn't use ro/di water in setup, you may really have a lot of phosphate. If you didn't wash your sand, yep, even more. So---how to get rid of the phosphate? Not a CUC. Either a refugium (an algae-farm) or a phosphate reactor (about 50.00 and highly effective, over about 3-4 months: do NOT expect instant results. Also DO NOT OVERDO: you need some algae for health and food for some species. Blennies need it; copepods need it; and your snails need it.)Sk



Hi Sk8r! I've read everyone of your stickies and have learned so much from them. Here's another great one to add to the list.

I plan on using Pukani live rock from BRS to start up my tank. I've read on a thread (not yours) to use a GFO reactor while cycling to help eliminate the high amount of phosphates that the rock can emit. If I do have a fuge in my sump, would I still need to use a reactor to help out while the tank is cycling?

Thanks for all that you do for us beginner's in the hobby. I greatly and sincerely appreciate it!

sponger0
06/15/2012, 03:17 PM
Hi Sk8r! I've read everyone of your stickies and have learned so much from them. Here's another great one to add to the list.

I plan on using Pukani live rock from BRS to start up my tank. I've read on a thread (not yours) to use a GFO reactor while cycling to help eliminate the high amount of phosphates that the rock can emit. If I do have a fuge in my sump, would I still need to use a reactor to help out while the tank is cycling?

Thanks for all that you do for us beginner's in the hobby. I greatly and sincerely appreciate it!

As I mentioned earlier, the size of your fuge depends on that. Ive heard in order for a fuge to be effective it has to be relatively the same size as your DT. But in proportion to that, if you have a 75 gallon tank and your fuge is 15...dont plan on it being very effective.

A phos reactor would be much more effective...but IMO I would let the tank cycle and wait for the phosphates to make them selves apparent. Im also a firm believer in not added corals into a tank until at lest 3-5 months running. Add fish but not corals until you know oyu have the algae or phosphates under control. Especially after my experience starting a tank with marco/pukani rock.

Sk8r
06/15/2012, 09:30 PM
A reactor takes about 3 months to really strip out phosphate from a 50, the cycle takes about 1-2, so you're likely still to have some phosphate left. Don't eliminate ALL phosphate and algae: your microlife feeds on it, and you can have TOO clean a tank, where it's all white and nothng lives.

mbd521
06/15/2012, 11:16 PM
another great post!!! thank for sharing your knowledge and experience sk8r!!! one day a long time from now, maybe ill be as knowledgeable!!!


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ChrisL1976
06/16/2012, 12:06 AM
You always have great Posts.

This is a time-lapse I made of my CUC working over a 7 day period. I never touched the tank.

http://s12.photobucket.com/albums/a220/chrisl1976/JBJ%2028CF/?action=view&current=CUC-TIME-LAPSE-1-1.gif

BrettH
06/19/2012, 07:40 PM
A phos reactor would be much more effective...but IMO I would let the tank cycle and wait for the phosphates to make them selves apparent. Im also a firm believer in not added corals into a tank until at lest 3-5 months running. Add fish but not corals until you know oyu have the algae or phosphates under control. Especially after my experience starting a tank with marco/pukani rock.

Sponger0 I have a slightly different approach in that I believe it makes more sense not to add any fish after cycling, or actually a very minimal amount so there is some minimal ammonia source. Here is why, by adding fish, you have to feed therefore will be adding phosphates when your are trying to mimize them during a period when you want as little phosphates as possible so that you can establish the "good alage". My goal is to get coralline algae established as quick as possible so it will out compete the nuisance algae and not vice versa. By taking this approach I will not only be out competeing nuisance alage with my refugium (75 gallons on a 240 DT)' but also with coralline. I would also think that as long as your tank parameters are stable and in the appropriate ranges after cycling, adding a few corals shortly after cycling is ok. I hope my post isn't coming off as argumentative. Just a slightly different approach.

@Sk8r excellent post about CUC. Spot on IMHO.

Cheers
Brett