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Will my tank support an octopus in its present state?

Jan 16, 2004
Hello all,

Please do not tongue-lash me for this question:

I have a tank that has been cycling for a little over two weeks now. It currently contains 25lbs of live rock (which I have been using to cycle it), and fine aragonite sand. I have mechanical filtration, and a remora skimmer. The water in the tank is entirely from my 75g reef tank (i.e. conditioned, mature water). The only reason the tank is now in the cycle process is because of the live rock. Parameters are as follows:

ammonia - 0
nitrite - .8mg/L
nitrate - between 3-10mg/L
temp - 78 (higher than normal to accelerate cycling)

Now, I realize that my tank is not fully cured. Although, the nitrites have been falling, and overall the system is approaching completion.

I've perused this site and have noticed that the "gold standard" is to wait three months for an octo tank to cycle/establish itself. Now, here's my question: what do you speculate would happen if I put a bimac into my setup three days from now (assuming nitrites would be nearly zero, and the nitrates fairly low)? Are octos more sensitive to water quality than fish? I can't imagine waiting three months, especially considering I used established water from my reef tank.

Thanks in advance--just trying to learn more about cephs.
well, you would get a spike in ammonia and then nitrite again and it all depends on whether your biological filter could cope with it???

If you dont have anything making up to be the same size as the octo's biomass.. ie ammonia production, just now then the filter wont cope.

i always recomend cycling with fish that can be taken out before the octo goes in and the fish and filter should have been operating at the same level as the octo will produce, so that on removal of fish and introduction of octopus kinda goes unnoticed to the filter bacteria.

using mature water and rocks etc does greatly speed up the process, but if the biomass (fish, inverts etc) that are in the tank is small then the filter wont cope with an octo being introduced..

hope that makes sense (it is early :bonk: :bonk: :bonk: )
Crevalle, I've found that quickest way to cycle a tank is too add "live" sand. Not that $30 a bag crap from the fish store, but sand that has been taken from an established tank. I had a 55g tank I was cycling to hold my seahorses, which had approximately 50 pounds of high quality cured live rock in it and a good 4 inch sand bed. I waited and waited, at least 2 months and while there was no ammonia, the trites and trates stayed off the chart for weeks. While visiting a local reef shop, I noticed he had 3 buckets of sand sitting in his live rock tank. This was sand he had taken from the bottom of the curing tank. I bought a 5 gallon bucket of it, brought it home and removed about half of the sand in the tank and replaced it with the sand I just bought. Within a week the trites had dropped to just a trace, and the trates were at 40 ppm.

Using water from an established tank really does little good as there is very little bio-activity in the water column.

Colin--thanks for the insight. The bio-mass balance you mention makes a lot of sense. Per your thoughts, I ended up getting a couple clowns (didn't want damsels in case they pick on the octo, and because they are hard to remove). I also threw in a chocolate chip starfish, although I may leave it in the tank.

Neptune--I have only tested for copper, which was negative (thank God). What other tests do you recommend? I am using R/O water as a top-off.

Spring--that sounds like an excellent plan. However, I'm just not sure where I could find good sand around here. I wouldn't want to take it out of my other tank, as it could disrupt/pollute my reef. I'll check around...
Ok, I have taken a turkey baster and transplanted some of the cc substrate from my main reef tank, to the future octo tank. Although, altogether we're talking maybe 1/2 cup of actual material. We'll see if it helps a little. The clarkii clowns appear to be doing fine, but I'll keep watching them closely.

Will water changes speed-up the process? I read that I could do some water changes, and it will reduce the nitrites, but the nitrites that remain will become even more toxic partly due to a probable Ph jump. What do you think?

to clarify a point :smile:

adding an amount of sand from an existing tank to a new tank will introduce the right bacteria to the tank and be a good starting point... but it will not cycle a tank or prepare a tank for an octopus unless the tank has a bioload similar to that of the proposed octopus AND has been allowed to mature for at least a few weeks to months to have zero ammonia, zero nitrite and near zero nitrate... i hope that makes sense what im trying to iterate???? :smile:

water changes will actually slow down the process, just let it get toxic and then settle down! Keep an eye on the clarkii for stress though!

You want to have enough bacteria living in your tank to cope with the octopus's waste.. so if you are getting a small bimac the clowns should be similar in waste output (depending on size) and as long as they come out immediately before the octo goes in the tank should be fine!

If for example you used one molly or got a big octopus or added a ceph before the tank matured, the bacteria present wouldn't be in high enough numbers to deal with the ammonia.

Colin--I understand what you're saying, and I'll be using it as a guide regarding when I will know the right time to add my bimac. Makes perfect sense.

Burstsovenergy--using water from an established reef tank actually does speed-up the cycle time, because the water contains smaller amounts of beneficial bacteria that is not present in freshly-mixed marine salt/RO water. It does not compare to adding something as substantial as established sand, however. I'm hoping the LR is a huge help in cycling as well.

So, as it stands, I've added two medium clarkii clowns, and a choco-chip star. I've added a small amount of substrate from my reef tank, and the temp is in the low 80s to spur cycling. My nitrites are dropping, and my nitrates are skyrocketing. So far, the clown is doing well and eating. Time will tell.
Joel--yes, I just read that last night. They also suggested that when it comes time to clean the filter, to do it in old tank water so as to prevent the beneficial bacteria from dying in the process. But yes, they said that transferring filter media will speed-up the process. Nice observation.

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