Upgrading to a bigger tank

m3rcfh · Jan 4, 2018

Guys, I know there are lots of threads out there on this topic but everybody seems to have different opinions (as most of things on this hobby

)... I'm just throwing my thoughts out there and looking for your input.. any help is greatly appreciated!

I have an established (about 7 months old) 40 gallon with some LPS and 5 fish. Recently I got a dirty cheap 75 gallon on black Friday and got that set up. New dry sand, new 40lb of dry rock and 20 gallon sump. Filled it with water, got the salinity and temperature right and it's running for 5 days now. Haven't done anything in regards of cycling, so no existing bacteria. My plan is:

1) remove about 50% of the water from the new, non-cycled, tank and store on a bin
2) transfer about 75% of the water from the old tank to the new one (only to help matching pH and chemistry)
3) transfer all the live rock from the 40 gallon (about 30lb before cured) over to the 75 gallon (they stand only a couple of feet apart) and work quickly on the aquascape
4) Transfer 1 or 2 cups of old sand from 40 gallon over to new tank and let it settle down for some minutes - maybe not even necessary?
5) transfer all the corals, CUC and fish at once to the new tank (about 30 to 45 minutes after live rock has been transferred), let them acclimate on a plastic bag
6) top off with water from the bin and save the rest for first water change
7) transfer current canister filter from 40 gallon to new tank for a couple of days to help the bacteria spread out? Or move media from canister to sump?

Note: should I pour in a bottle of Dr Tim's in between steps 2 and 3 for safety? I know there's a lot of back and forth wether it works, but more bacteria can't be bad, right? Or would it crash with the existing bacteria?
I want the fish and corals to suffer less stress possible (I guess we all want that).

I got a Seneye and will keep an eye out for spikes of ammonia during the first weeks... not adding new live stock to the tank for a while, just creating a better environment for the current ones...

Thanks in advance for any ideas you might have!

DLHDesign · Jan 4, 2018

Any time you disturb that much of a tank, you're likely to stir up a lot of debris and such that have been "stable" in your current tank, but would be less so in your new one. As such, you can expect at least a "mini cycle" during something like the above. Even though it may be a smaller cycle than a normal one, it could still be enough to harm your fish and corals. They may make it through just fine, but it may also be enough to cause a chain reaction that could crash your tank...

If you have the ability, I would suggest patience and a slow approach, myself. Give your new tank time to fully cycle as normal, then transfer things over once the cycle is complete and parameters match. At the least, I would match salinity and temp between the tanks so that you don't have to float any fish in bags (just remove from one and add to the other).

Did you cure the new dry rock already, by chance?

m3rcfh · Jan 4, 2018

I rinsed the dry rock throughly and added it to the new tank. Haven't cured/cycled them at all - honestly I didn't think it would be required as I got dry caribbean rock from BRS.

Initially I thought in transferring over some of my live rock to seed the new tank and just ghost feed until cycled. Or even using the magic DR Tim's to complement the bacteria and transfering only a pair of clownfish instead of ghost feeding and watch the ammonia level. Shouldn't be too bad on 2 small fish only instead of 5 and corals.

I guess I ended up going back to transferring all at once as I planned on my first post just because I'm not sure if removing some of the live rock will compromise the existing balance on the 40g. Maybe removing some dryrock and the clownfish will lower the ammonia production to a level that the remaining live rock on the 40g can filter for the other 3 fish, but it's impossible to know for sure.

I guess the best way is cycling the new tank, and slowly transfer the 5 fish over in steps... as it would be a new tank and the fish coming from a LFS. But wouldn't transferring the live rock after the new tank is cycled also cause a mini cycle as I'm still stirring up all the bad stuff currently "standing by" on my existing tank? I feel like any direction will cause a mini cycle

Brew12 · Jan 4, 2018

Last month I tore down a 120g tank, put all the fish, coral an live rock in 5 totes, and set up a new 187g system in its place. Added new sand, filled it a good way with water and got it up to temp. I then transferred all of my rock and coral into the new system and put the fish in it. The entire process took around 30 hours. All my fish and inverts made it.

One thing I did was use a small pump to blow as much crud out of my rocks as possible. I used a canister filter and filter socks to clean out the debris. As @DLHDesign points out, stirring things up can cause a nutrient spike/mini cycle. I made sure my rock and sand were as clean as possible prior to starting.

You have better options since your tanks are side by side but the core of your plan is sound. Cycling the 75g tank gives you more of a safety margin and isn't a bad idea. Either way I would get the rock in the 40g as clean as possible prior to moving it.