Hello,
You are going to need more circulation for this tank. I highly suggest at least a couple of power heads (this may be against the forum rules, but I would advise AquaClear 402's, they are virtually indestructable. MAKE SURE YOU INSTALL PRE-FILTERS ON THESE, as well as the intake for your Fluval) in addition to the Fluval. One of the advantages to a sump is the ability to turn over a high rate of water per hour thereby saturating the water with oxygen. In addition, a sump provides the opportinity for evaporative cooling, as well as increased water volume which lends itself to a more stable environment for your inhabitants. I strongly advise the use of one in your next tank. That having been said, if you are going to go with an octo, it will be necessary for you to secure the top of the tank and as a consequence, limit the natural gas exchange which occurs at the surface of the water (contrary to what some believe, good water circulation is much more important for proper oxygenation of your tank water than an air pump.) Maybe some of the other members can put their two cents in on this, but I would advise you use a very small diameter drill bit (1/8"?) and drill a bunch of holes in the plastic strip which is typically found along the back of a glass top (I am assuming you have this type of lid). Make sure that the current generated from the powerheads create some turbulance on the surface of the water as this is the primary interface for gas exchange in your proposed set-up. Which model of Prizm skimmer are you going to use? Please advise. Ad your sand first (not the live stuff yet!) then your water and then your salt. After several days of good circulation at the proper salinity, ph, and temp, you can then add some good quality, cured (if it smells like rotten eggs, it ain't done yet!) live rock, as well as five or so pounds of live sand. Beware the temptation to fill your Fluval to the brim with carbon. A little carbon goes a long way, perhaps a cup or less in a pleated filter bag specifically intended for this purpose. Too much carbon can have an adverse effect on water chemistry in that it can cause your ph to flux to the point that it would hurt a delicate animal such as an octo. Change the carbon every three weeks or so as it will have exhausted its' ability to adsorb the organics you are trying to keep to a minimum by then.
I know this info may seem a little daunting, but keep in mind that you are trying to mimic an environment that has taken roughly 4 billion years to evolve; you can't expect to absorb all of this in one shot. The information the members at this site can provide for you will prove invaluable should you choose to do your reasonable best to care for these creatures. In the short time I have been visiting here the members that I have corresponded with have made me feel very welcome. I am sure others will ad to this thread; some may not agree with my recomendations, but the more information you aquire, the better you will be able to make educated decisions. The best of luck to you
