How much flow is too much?

[gabbagabbawill]

I have two Koralia 4 pumps along with a 1800GPH return pump pushing ~1200GPH.

The koralia's are on opposite ends of the tank. The return pump branches into four outlets into the display, and those are mostly aim to disturb the surface of the water, with some flow bouncing down the front of the glass...

It keep detritus off the sand bed. The sand bed is also not being blown around.

My biggest concern is the fish... they seem to be fighting the current a lot. They seem to have gotten used to it, but I wonder if it is too much because when I turn off the pumps, they explore the entire tank and move much more gracefully about. They seem happier with it off... but flow is a good thing... I don't have a ton of rock just yet, so I wonder if maybe I just need more rock to break up the flow or do I have too much flow for this 120 gal tank?

Here's a photo:

http://photos-d.ak.fbcdn.net/hphotos-ak-snc1/hs090.snc1/4930_1181156850327_1270372888_30517315_5790209_n.jpg

Thanks for your suggestions.

[manuelink]

i´ve seen that the koralias 4 are to rude in this aspect
and might your circulation is good but the fishes whose their swim is slow will got problems in this aspect
put your koralias looking to up at center and play with the pumps moving the koralias until the sand doesnt move

or if its imposible, sell the pumps and buy the 3´s

[gabbagabbawill]

I wish I could just turn these pumps down a little...

So, you're suggesting putting them lower in the tank and pointing upwards?

What about on the back wall and into the glass?

I really like how they stir everything up... just wish it was slightly more "gentle".

any other suggestions to tame them just a bit? I read a lot of places where people thought the 3's were too little flow...

[kovuu86]

I have a k4 in my tank, and i feel if i put the extra tip on the powerhead it makes the flow a little gentler. Also, i think the fish will get used to it. If you have fish that dont swim much liek firefish, the will find an area they like.

[suasponte2/75]

I have 2 x TUNZE 6100's (approx. 3100gph each) and a Dart (approx. 2000 gph) on the closed loop and a MAG 1200 (900gph) return and still think I don't have enough flow ;). My fish also "play" in the current every once in a while and don't even seem concerned about the flow. Imagine how much flow there is in nature on a real reef. We can't even come close to those gph's that mother nature can provide. I think you're fine and possibly will need more flow in the future me thinks.

[Michael]

2 k4s is not too much for a 120, its all about positioning, the ocean is a lot more ferrocious than a couple of k4s, what i have noticed is you seem a little low on rock, if there was more in there the flow wouldnt be so aggressive and there would be quieter spots, plus your biological filtration woould be a lot better

[LobsterOfJustice]

It will change once you have rock. Rock not only blocks flow, but can help create interesting patterns as it blocks flow.

Positioning also makes a huge difference. My rock is arranged in two islands which are not touching the front, back, or sides. I used to have my tunzes positioned in the back corners pointing at the opposite front corners. My fish needed to avoid a large section of the tank otherwise it's like standing in front of a firehose. Now I have the tunzes pointed directly at each other across the back wall (only one on at a time). This way I am not really using the direct output of the pump to produce my flow, but it's undertow and net displacement. When a given pump is on, it pushes a lot of water at a high speed across the back of the tank. Because of displacement, and because the water hits the other wall and has to go somewhere, the entire rest of the tank undergoes a gentle but sizeable sweep across the entire tank in the opposite direction. The added benefit of this is that it causes the fish to hang out in the front of the tank as well (or rather, just avoid the back 5" or so).

Kind of hard to explain... but I hope that makes sense. While I agree that "you can't have too much flow", you can have it positioned wrong. You might be making a lot of your tank space unusable by using strong, direct flow. If you need flow in a certain spot, you don't necessarily need to point a PH at the spot to get flow there. Take a few gallons out of your sump so the return just barely starts sucking air and fills the tank with bubbles. Then sit down in front of the tank, watch the flow, and start moving things around so you have the least "primary" flow (direct powerhead output) and mostly "secondary" flow (diffuse flow after bouncing off a wall, displacement, undertow, etc).

[Imzadi]

I thought this was a good idea, Lobster... so I set a straw in the sump, until it just sucked a little air... and watched the bubbleshow. Well, now it lookes like christmas in my tank!!! lol. I sure could see the way the flow manifested itself... very cool idea... now I just have to get rid of all these BUBBLES!!!

:-)

I agree though it is more about the direction of flow, as it about the amount of it. I have a 55g, with 2 x K3, 1 x K2, and a mag 9.5 return to a 3 manifold lin-loc thingy. And although there is TONS of GPH on paper, the rocks (and I LOVE my scaping) still create the 'dead zones' of sheltered area. There are 'rapids' that the evil little damsels ride like a water slide... and then the sheltered spots give a lagoon effect, that usually tends to collect the crap in the tank (food and poop), so they go there for a snack and a poop. I have the Ks aimed right at my rock, so that it flushes through it, so I bet I am hurting my over all GPH, but I think I want to get a couple of the Hydor Nanos, and stick them in the top corners. I can afford to take a loan out for the Tunze, and I don't want giamormous K2-4s on the front of the display... so I hid the bigguns in the back, behind the rock, and will put the wee ones out front, so there are less poopzones.

Hope THIS works.

[gabbagabbawill]

Lobster! Thanks, you've given me some great feedback. I'll try that.

I do plan on adding more rock as I go along, rather than buy a whole lot of rock all at once, I'm working on a budget and putting in about 5-7 lbs every other week or so...

[Stripe01]

You need much more rock! Those current pieces just look like rubble.

[somedude]

i have often wondered about this as well.

i don't want to hijack a post, but could someone answer...about what turnover rate should we aim for in a sps dominant tank?

~alex

[monti1]

I had 2 vortech mp40w and 3 k3 in my 120 an still had a few dead spots. I all honesty it is very hard to have too much flow. It is all about figuring out where to aim the currents.

[gabbagabbawill]

stripe... maybe they look like rubble but most of those pieces are about 6-10" in size (the tank is 5 feet from end to end). I'd call rubble 2-5" size... but that's just me.

But like I said above, I am working on adding more live rock... no need to rub it in!!! :p