Water movemement in a reef tank is probably one of the most misunderstood aspects of reefkeeping.Seems many setting up tanks are worried about lighting and skimmers where water movement seems to get pushed on the backburner as a later "upgrade".You can grow corals with 4x40w NO flourescents useing $5 GE6500k bulbs in a tank with proper current and have a beautiful tank free of nuissance algae.On the flipside,a tank with poor water movement,an $800 DE MH lighting fixture and a $400 skimmer will endup with nuissance algae problems.
Many talk about 30x or 40x for turnover rates and it means nothing in terms of the velocity/type of current a particular tank has.I have 43x turnover rate on my 40breeder.Some would suggest that turnover is adequate for a high flow,SPS(bad term)tank.I keep Faviids,Musiids,and Euphyllia spp. in what i consider a moderate current tank.
Creating mass flow doesn't have to be too expensive.With the use of oversized plumbing to lower head pressure on return pumps,you can gain up to 25% more flow from your pumps.Dual oversized returns,closed loops,return manifolds,high gph powerheads like SEIOS are all good ways to move water and can be tweaked to achieve slower velocity.
The last thing i'd like to meniton is having mutiple water outputs(returns,powerheads,etc..).You can have a 2000gph sump pump on a 55gal tank and if you only have dual returns,your going to have dead spots in the tank.I'd recommend at least 4 outputs for any tank 3' long or smaller.With 4' tanks,the minimum i'd use is 6.This is highly variable and is by no means a rule.Wider,deeper tanks will obviously need more outputs than shallow,narrow tanks.
david, good info ... i'm getting some good ideas for when i get my mag 7's ($15) and MH lights (2x250w $200). i had to throw the buying price in there to make you sick. lol
As long as you dont have dead spots(low to 0 water movement)in your tank,then your fine.Assuming you also have a sump return on your 55,that puts you at 4 total outputs for water movement which is usually fine on a narrow(12.5"Wide) tank such as a 55gal.
Water movement in a reef
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