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New Tank Ideas


Dec 22, 2004
Happy holidays everyone,

I've been thinking about getting an octopus for about a year. I set up a 30 gallon tank with clownfish and live rock at that time to get some experience with saltwater.

This fall I picked up a 75 gallon tank for a good price and have had it sitting in my porch because I couldn't afford to set it up until now. I think it would make a good home for a bimac from Octopets. This tank is considerably larger than anything I have experience with, so I'm seeking a little advice.

I was thinking about setting up a ~ 20 gallon sump/overflow in the tank stand. I'd like to have a protein skimmer and my heater in the sump. Instead of baffling it and making the sump itself the filter, would it be easier just to hang a couple powerfilters on the sump? I'd have to make sure that my flow through the sump was at least as much as the flow through the filters.

Does this sound like a good idea, or should I do it more conventionally and just make sure there's room for the heater and skimmer?

I understand that the octopus produces a lot more nitrogen than other critters. Would I be well-advised to build a denitrator?

Those are all the questions I can think of at the moment. Any advice is appreciated.

Hi Dan and welcome to TONMO.com! :welcome:

With a protein skimmer in the sump, your tank will probably be warm enough for a bimac without a heater (unless the room it's kept in is very cold). Most of us have had more of a problem with heat than with cold.

I'll let our tank experts answer your other questions.

I was planning on just using the heater during the winter months. I'm the kind of student who's extremely stingy on important things like food and warmth but ready and willing to overspend on crazy hobbies.

I do have a number of questions about setting up the sump: From what I gather I am looking for a submersible pump that will recycle the tank 4 or 5 times per hour at the given hydraulic head? I then need a HOT skimmer/siphon that has a little more capacity?

Do I set the output from the pump low in the tank to circulate better?

Any input much appreciated!

I think most of us have the return outflow towards the top of the water. I have an Oceanic Systems tank and it allows some adjustment, but basically near the top of the water. Although octos like lots of oxygen, they don't need strong currents.

By the way, sometimes they like to play with the outflow. My bimac used to inflate her web by hanging on the outflow. She seemed to enjoy it. Did the same thing with the powerhead.

We recommend getting an over-rated skimmer because octos can be very messy and you'll need it to remove the ink in case of inking. Mine is rated for a tank three times larger than I have.

Have you looked at Colin's Equipment article?
Cephalopod Care
or click on the Ceph Care button above.

a denitrator might be usefull but not altogether necessary... why not think about having the 20gal sump as a refugia with a reverse light cycle to the tank and harvest caulerpa from the tank to remove nitrogenous waste?

You could also have a deep sand bed here safe from the octo's activities. Normally i advise against DSBs for tanks because they can crash after a few years but we dont have that problem with octos... unfortunetly :frown:

The sump is a great idea and with some live rock and a good skimmer you may only need a carbon filter in case of inking.

After reading up on some web resources, I really like the idea of having a in a deep sand bed. Its nice from an aesthetic standpoint to have a complete nitrogen cycle with anaerobic reduction.

I would still need mechanical filtration. Would you recommend hanging a powerfilter on the sump or would I have enough room in a 20 gallon sump to have adequate sand bed area and a couple baffles with media and carbon?


I'm sorry Colin, I didn't see where you said I may only need a carbon filter.

This is good--I could set the whole sump up as a sand bed and then if additional filtration proves necessary, I can add a powerfilter.

yeah, i think that would be a good idea...

can you get a couple of hadfulls of sand from a mature tank? If you added that to your sump it would speed up the maturation process and add some beasties that will help in the sump too.

Perhaps add a couple of bits of live rock for the same purpose.

Have the water pass through the skimmer directly from the tank before the sump as the skimmer will remove a lot of the waste before the filter/sump needs to worry about it.

The carbon doesnt need to be in the tank the whole time. Just maybe a few days a month will help polish the water and that is more chemical filtration than mechanical.

Unlike a reef tank you will need to do more frequent water changes on your tank, but you wont really know until it is up and running with an octo, each tank is different.

The reverse light cycle and caulerpa algae in the sump helps maintain even pH levels day and night, and increses night time O2 levels which can drop.

In my smaller saltwater tank I have carbonate gravel rather than sand. It is, however, brimming with life and I was planning on putting a little bit in to help the cycle along. It amazes me the kind of stuff that's in there: tiny shrimps, bristle worms, and at least a couple hundred tiny brittle stars.

Hi Dan
thats great, it'll help kick start a new tank.

Its one of my favourite things about this hobby; by adding live sand and live rock you never know what you may get and each tank is quite unique :smile:

I'm planning my sump now. I picked up a 20H tank and a protein skimmer. The water would enter the skimmer chamber (12 x 7") from the overflow and from there over a divider into the sand bed (12 x 16"). Since the skimmer has its own pump that sucks from the bottom, I could put carbon or mechanical filtration (if it proves necessary) around the skimmer in its chamber.

Does this sound like adequate size for the DSB to be useful in reducing nitrates? Since the sump is 16" tall, I was hoping to have a good 6" sediment depth.

dpending on what kind of substrate you use you may be able to have 3 - 4 inches of DSB, finer sands dont tend to need to be so deep. You may want to have a baffle of some sort to slow the water down from the skimmer to the refugium? Oh wait, think your divider will do that?

A good tip will be to use RO water and that way it will be resonably free of nitrates and phosphates to begin with...
One last question: I'm building an overflow out of PVC instead of drilling the tank. I'd like to paint it black so that it is a bit more subdued and matches the back of the aquarium (which has been painted black on the outside). I did a google search and found that the koi people use a special Rusoleum PVC-based paint in their ponds. Do you think that paint would be dangerous in the tank even though it is vinyl?

I was planning to use DI water for the tank since I have an unlimited free supply of it at school. Is there a qualitative difference between DI and RO water that makes RO considerably preferable?

okay, you got me there... i have no idea whether it would be safe in the tank or not... saltwater can be much more corrosive and can bring out the worst in plastics. But i can tell you that if it were me i would either get the dark coloured pvs pipe or box it in outside the tank...

either RO or DI water is fine,


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