Water amounts for raft

[Chelsea Brannan]

hello!

the hubby and I are setting up a 2 rafts that are 4x16 ft. (later in summer we will add on if the first two go well). We have never built them before, just media bed systems currently. We 9 IBC totes that we can use, but if each trough holds 300 gallons of water, and the totes 275 we thought each raft would need to use two totes for water. Is this right?  My concern is when all the water is in the raft system...whats left for the fish tanks?  I know there is an easy answer to this, but I can not wrap my head around it right now! I have been starting seedlings and cleaning totes and busy building a chicken coop, so I havent had the chance to really think this through! Any help would be greatly appreciated :)

[Vlad Jovanovic]

A 4x16' raft filled with 10.5" of water is about 418 US gallons...

But I'm not quite sure that I understand your quandary..?  The rafts will have a pretty constant amount of water in them, won't they? If you describe your set up...or how you plan to set it up it might help in understanding the nature of your concern...

[Chelsea Brannan]

ok, lets see...i will have the fish in one ibc tote, and the raft trough will be full of water. Should I have a second tote full of water so the level in the fish tote stays full? Or is it really needed? (i'm sorry for the confusion, thats part of my problem, lol!)

[Vlad Jovanovic]

Ok, so if that system will be comprised of one fish tank and one raft...No, you really don't need a sump tank in that case. Just put the pump in the DWC trough (raft) and have an over-flow pipe at whatever height you want in the fish tank.

[Chelsea Brannan]

Ahh ha! Now, when we add the second raft trough (the same 4x16 ft size) we'd like to join the tanks and pump from the last trough back to the tanks. We'd like to use one pump only in the system. We're thinking of adding a swirl filter in the form of a 55 gallon barrel. I was thinking that I could have the fish tank water gravity feed into the swirl filter which would then drain into the raft troughs. Would this work ok? Do we need a swirl filter? Thanks for your help Vlad, I'm glad to have your advice. 

[Vlad Jovanovic]

Sure, that would work. Having some kind of mechanical filtration before your DWC troughs is a really good idea...whether that be a swirl filter, or a media filled grow bed, net tank of some sort, or any combination thereof. I really like the idea of using a worm filled media bed as your main filtration element, since fish food is not the cheapest plant fertilizer you can use...and the way fish food is made kind of irks me, so I want to get the most out of it and not be removing those nutrients from the system if I can help it. Also, it just seems like a good idea to have a stable dedicated bio-filter, not necessarily a necessity, but it might make your AP life a bit easier. 

[Chelsea Brannan]

yea I figure we needed filtration of some sort, I'd love to add a media bed in combo with the raft systems perhaps later when I can afford to buy all that media, haha!  We're looking to make each raft trough an inch or two lower than the preceding one in order to help with gravity flow of water. If my in-flow of water from the ibc totes in 2 inch pvc pipe, should I use the same size between the troughs or go with a 3 inch? 

[Vlad Jovanovic]

You don't have to use hydroton/hydrocorn...regular old rocks will do as long as they don't contain limestone (or at least not very much CaCO3)...many people here seem to be pleased with expanded shale...you could check on prices in your area...

2" pipe should be fine...you might want to look into using a bridge siphon to connect the two troughs...could be an interesting (and perhaps cheaper/easier) way to connect the two...

[Chelsea Brannan]

ah yes, a bridge siphon! I will look into that one for sure!   Have you ever used one? My raft trough will have about 1 1/2 ft walk way between them, i'm not sure that bridge will be the best. I was just going to connect them them with a length of pipe....have to research more I guess :)