How to Decomission a marine tank setup?

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[Canoe]

A friend is downsizing and the marine aquariums have to go. I've been volunteered to do the tear down work.
He's got a 125 gallon six foot FOWLR, with around 150 lbs. of live rock from one end to the other up the middle. Lots of coralline, but not all surfaces yet.

Inhabitants appear to be healthy and are active:

• two clowns
• four Azure Damsels, that are very purple-blue on top
• a file fish
• a shy but fat Spotted Green Mandarin (that has grown well and looks downright chunky with all the pods it's getting)
• a Goby of unknown type (Rock?), a varied dark brown, that's cautious yet inquisitive (he'll hide in the rock, yet come out on the sand to follow me down the tank to see what I'm doing), liking the bottom of the tank, both on the rocks and digging in the sand near the clowns just to keep them busy (they'll chase the Damsels away but appear to enjoy teasing the Goby). Occasionally he appears to be shifting pods out of the sand.
• two sea urchins

The thought is that we can use the spare 48G bowfront as a BB quarantine style holding tank for the fish while they wait for new owners, freeing up the main tank for decommissioning for sale/moving. It has an external circulating mechanical filter and a HOB skimmer. Will have many PVC tubes for hiding places. To bring the 48G up and running, we're thinking that (similar to keeping an air-pump on a sponge going in a sump or DT in reserve for a QT) we'll get the biologicals going in the filter by running it on the 125G, then transfer it to the 48G, followed by an unknown time to cycle?

The live rock from the main tank will be transferred to a heated bucket with a powerhead for circulation, freeing the main tank for cleaning.

Once new homes are found, I intend to take the 48G to my place to keep the clowns, which I'll keep in a quarantine tank while I cycle the 48G with live rock.

We're concerned with:

• will everything be healthy in a bare "quarantine" 48G? Should it be partitioned to keep them separate?
• how to keep the mandarin and goby fed (live food ?) as they're accustomed to tons of pods to get fat on?
• are the fish better off to be moved to new owners directly from the main tank? (but due to timing of selling house, we may not have a choice)

Somewhere we heard to freeze old sand before washing/cleaning, to ensure all biologicals are killed off.

And, any other points, suggestions, concerns, or best practices for decommissioning a tank.


p.s. How do we tell that potential new owners of the mandarin and goby do in fact have a mature tank with pods?

[Malyon18]

Well first off I think the easiest would be to sell the fish from the main tank but with the time constraints the 48g may work, have you thought of putting some of the LR into the 48g to help cycle it. I believe that if you moved some of the rock and used water directly from the 125, there would not be much of a cycle if any at all. Try listing the fish and see how fast they sell. As for the mandarin you could ask for pictures (which may be a hassle) but you will probably be left with having to take the buyers word for it.  Other then that the rest of your ideas make sense to me.

[Dakotamay]

I agree with Malyon.
You should put some live rock. At least 30-40lbs of it into that 48g. What you want to make certain you do is use the water from the display tank. More importantly to observe is to drain off the water you need before you take rock out of the big display. Taking the rock out will cause all sorts of nasty stuff to be released from the substrate and will pollute the water. Get your water out first. Then select your live rocks for the 48g. The rest is fine in a heated and circulated bucket. Just heated won't cut it. Put a power head in there too.
They all live in the tank now. So, I would suspect they should be all fine. But, moving down into a smaller tank might cause some issues. You'll have to watch them and see.
As for the mandarin and goby. I'd try and sell them first. They aren't going to have enough food in that 48g. They'll just starve.
How can you tell if the potential buyer has a sufficient enough pod supply?  Easy. Here's a couple things to ask and what you want to hear them say.

1. How long has the tank been up and running? 
The tank should of been up and running fully cycled for at least 6 months or more preferably a year to establish a good pod population to sustain 1 yes 1 either mandarin or goby.

2. How many pounds of live rock do they have in their display tank?
They should have 75lbs of live rock per mandarin or goby they intend to keep.

3. Do they currently see pods running around on their glass during the day or only at night with a flashlight?
A tank with a good pod population will have pods visible all times of the day.

I can't think of any other things to ask at the moment.  I'll repost if I do. Though what I've listed will give you a pretty good idea if the person knows anything at all about keeping a mandarin or scooter goby.

Also, try putting some food into a low flow area of the tank. Where you see the mandarin and goby hanging out. They may just have learned to eat prepared foods. In which case you still want to make sure the potential owner has pods in their system but not as much of a concern as the fish will eat prepared.
I had a mandarin and a red marble scooter blenny (goby) that both had learned to eat prepared foods. Sadly when we moved from our 75g to our 180g we did it too fast and crashed the 180g.  Losing almost all our fish including my beloved Manny and Scooty.

Would love to have said I'd take them myself. But, I don't feel we're quite up there in pod population yet only having been stable for 2 months now.

Good luck

[Canoe]

Ahh.
Taking water and some rock from the 125G to the 48G makes more sense:

• I can get the 48G's pump/filter primed on the 125G,
• move some water & the pump/filter to the 48G,
• transfer some rock (carefully from the top of the 125G to minimize silt/disruption),
• transfer additional water every few days (it will be like a water change for the 125G), until the 48G is full.
• then when the numbers confirm the 48G has cycled, transfer the fish over to same taste, salinity, temperature.

have a quicker cycle and more stable and healthy 48G for a holding tank.
I assume still have the PVC tubes for extra hiding spots. Can't do any harm.

Thank you!


Looks like I should get permission from my friend to put the Goby and Mandarin up for sale sooner, rather than later.

[Canoe]

• a Goby of unknown type (Rock?), a varied dark brown, that's cautious yet inquisitive (he'll hide in the rock, yet come out on the sand to follow me down the tank to see what I'm doing), liking the bottom of the tank, both on the rocks and digging in the sand near the clowns just to keep them busy (they'll chase the Damsels away but appear to enjoy teasing the Goby). Occasionally he appears to be shifting pods out of the sand.

... I had a mandarin and a red marble scooter blenny (goby) ...

Thank you. Googled photos. This Goby is actually a dragonet, or brown Scooter Blenny. I can't believe what a fun little fish this is. I would never have guessed. I too wish I had a mature tank for it...
Makes me consider ditching the planned BB for sand, just to be able to eventually get one of these.

[Dakotamay]

They are a funny little fish with huge personality. Our little red marble scooter blenny used to come up to the front of the tank and wave to our 7 year old son. He was so proud he taught the little fish to wave lol.  When she wanted attention from me she'd dance at the front of the tank til I came over and talked to her. Just packed full of personality.
Our Mandarin, he would come to the front of the tank too. But only when he'd decided he was hungry and wanted some food lol. When he came to the front of the tank looking to be fed. He'd show you his belly. As if to say. See this, I'm hungry lol. I always was able to ensure he was nice and plump since he willingly showed me his belly.
I can't wait til we can have our mandarin and scooter again.
Yes certainly do put the mandarin and scooter up for sale asap.

[bt]

I believe that if you moved some of the rock and used water directly from the 125, there would not be much of a cycle if any at all.

Moving the rock - yes.  Moving the water - no.  There is nothing magic about "cycled" water (and nothing cycled about it either).

Not to say that using the water from the 125 is a bad idea.  It certainly has it's upsides compared to mixing up new water - not as harsh as freshly mixed water, don't have to worry about matching salinity and temperature or having to acclimate the fish, and just downright more convenient.  But it won't affect the chances of there being a noticeable cycle at all.  It is a good idea - but far from a critical step.

You could just as easily use new salt water, though.  As long as you let that water sit long enough first to lose it's harshness and acclimate as you go (if the salinity and temperature don't match), it wouldn't make a difference to the fish.

[shaheed]

Just a question for my own learning purposes.  What if the live rock was transported in the tanks water, and then placed in the bow tank?  Would there still be a cycle?

[bt]

Purely from a technical standpoint - yes.

From a practical standpoint - maybe, but probably not.

The second the rock hits air there is die-off.  Once back in water, that die-off will decompose and raise the ammonia levels.  But fully cured live rock from a mature system, with care taken to minimize exposure to air, not left in buckets too long (without heat, circulation or an outside source of ammonia) and placed in a new tank would have such minimal die-off that there should be more than enough of a bacteria population to handle that little bit of extra ammonia.

A cycle technically occurred, but with levels of ammonia so low that a hobbyist test kit wouldn't register it.  It could easily be less of a spike than what you would get from adding a new fish or overfeeding once.  Thus, practically speaking, the equivalent of "no cycle" to us.

There would be a temporary decrease in the bio-load it could support, though that could also be very minimal and would recover as the bacteria population recovered.

Also technically speaking, the cycle doesn't stop.  If it did, ammonia wouldn't be processed into nitrite anymore and everything would die.  It's an equilibrium in that ongoing process that is desired.

[Canoe]

...But fully cured live rock from a mature system, with care taken to minimize exposure to air, not left in buckets too long (without heat, circulation or an outside source of ammonia) and placed in a new tank would have such minimal die-off that there should be more than enough of a bacteria population to handle that little bit of extra ammonia...

So, like the companies that move your live tank in one day? Water and rock moved in coolers I believe to keep temperature variance to a minimum?

And in my case, across the room only from one tank to another? And I have the luxury of leaving the fish in the old tank while the new deals with any mini-die-off.

I can lower a properly clean and contaminant free small bucket into the main tank and transfer the rock piece by piece entirely covered by water. Is this overkill or worthwhile?

If I understand right, I won't need the skimmer running on the 48G until there's fish in it. I guess I should add it to the 125G to get it slimed so it's ready to work right away when transferred to the 48G?

[bt]

I'm not sure I stressed just how minimal it could be.  Across the room would be fine without needing buckets.  Don't leave the rock sitting out of the water if you can avoid it, but you wouldn't even need to really rush.

I'd move the fish into something temporary, move the rock, then put the fish into the 48G.  If you've got sand to deal with in the 125G, moving the rock will stir it up and pollute the water which would not be good to leave the fish in.  If you don't, the fish will still poop, which will cause a bigger ammonia spike than the die-off would.  Have some Prime or Amquel on hand if you're worried.

I'd run the skimmer right away.

[Dakotamay]

+1 bt

[Canoe]

Thank You!

[shaheed]

Thanks bt.  And canoe, hope you don't mind me semi hijacking this thread..!  I didn't want to start a new thread on what's already kinda being discussed here.  Which brings me to... More of me.. Lol

What if rock from old tank is transferred to new tank that now has new sand and some extra new dry rock?  This new rock and sand will go through a cycling/maturation phase.  However the bioload remains unchanged from previous tank.  How minimal is this new cycle, if minimal at all?

[Dakotamay]

The cycle will be minimal as the mature live rock contains your beneficial bacterias that will multiply quickly to catch up and colonize the dry rock and new sand.

I'd still give give the tank a little time and check the levels. But, I wouldn't expect you'd get levels high enough to be dangerous to fish or corals.

[bt]

What if rock from old tank is transferred to new tank that now has new sand and some extra new dry rock?  This new rock and sand will go through a cycling/maturation phase.  However the bioload remains unchanged from previous tank.  How minimal is this new cycle, if minimal at all?

Bigger tank, with all of the old rock being transferred?

If so, the cycle should be very minimal.  Likely fine for the same bio load, as long as it wasn't borderline already.  Keep an eye on the ammonia levels, but the fish would be better in the tank with the rock than a tank without.  Ammonia may linger in the water a little longer due to the higher volume of water for the same concentration of bacteria, but it would also be less concentrated.

[Dakotamay]

If you're moving to a larger tank. The smartest thing to do is to move all your rock and water. Then slowly over the course of a few weeks add new water to fill the tank and sump completely. This way it's like doing weekly water changes, except your filling.

[bt]

I wouldn't move the water if there is sand being stirred up in the old tank.  More likely to cause trouble than to help.

If it's moved before anything gets stirred up, then it certainly wouldn't hurt at all.

[shaheed]

Thanks Dakotamy and bt.

Yes transferring to a bigger tank.  I'm moving soon (few months) and will start a min 40g tank.  Maybe 60-70g if budget will allow otherwise 40g no sump.  Right now I have a 10g bare bottom.  Basically just wanted to start something.  I have ~10lbs of live rock in there, and a few fish -- nothing big... Really just 'seeding' if anything.  Transferring that amount of water with another 10g of 'fresh' saltwater and then maybe add more and more water week by week to fill up whatever tank I eventually get.