Reef flow rates discussion

snakeblitz33

snakeblitz33

Well-Known Member
Seriously.
There are many people here to advocate very high flow rates for certain types of corals and to keep detritus from building up and dead spots and all kinds of things and reasons of why to have such a high flow rate. However, is it the flow rate that is important, or the flow patterns?
First,... lets examine the general rule of thumb
GPH turnover rate should be 10x to 20x the volume of the display tank.
GPH turnover rate through the sump should be 2x to 10x the display tank, with an average being 5x.
So, does this mean that you can throw in a couple of powerheads in the tank to get your internal flow rate at the right GPH? Does this mean you are going to have a healthy tank? If your sump has a turnover rate of 2x, is that worse than 10x should one push more flow through your sump simply because more is better?
Types of flow and flow patterns...
linear = squirt gun, like an unmodified maxijet powerhead
nonlinear = maxijet with an oscilator
turbulent flow = two linear powerheads pointed at each other
surge = surge tank dumping into the aquarium
wave = back and forth motions like what tunze and vortech powerheads can create.
So, how can we use our knowledge of flow patterns to create an environment in which nutrients are carried to our corals, while CO2 and waste are carried away from our corals and are filtered out of the tank. Does this mean that we have to have a massive amount of flow in order to do this? No.
Sandbeds can, do and will accumulate detritus, mulm, and excessive amounts of nutrients that break down into nitrogen gas and hydrogen sulfide under anaerobic conditions - sandbeds either have to be maintained mechanically by gravel siphoning or biologically through introducing bacterial colonies, and microflora and microfauna to help break down these nutrients aerobically. So, no matter how you want to get around it, a sandbed has to be maintained. This does not mean, however, that flow patterns should not include areas of the sandbed.
linear powerheads are best used to direct detritus into your mechanical filtration system. Simply put, this means that the use of a powerhead can be used to blow water across the surface of the water to make sure that water is directed towards your overflow box or HOB filter. They can also be used behind rock work to help keep detritus from building up in the sandbed.
nonlinear powerheads are often times used to create a wave pattern without being an actual wave. It gives corals a brief moment of peace before the next "wave" hits. This helps the corals rest, just as they would in the ocean.
turbulent flow patterns are almost a thing of the past - and is used only in rare instances since new wide flow pattern powerheads have been made (koralias, etc.)
surge tanks are often times not applicable in home aquaria unless you have a lot of room and/or a built in wall tank and/or no spouse. lol. Surge tanks do have their place, and they do create large amounts of turbulent flow that can stir up more detritus than a regular wave maker can.
Wave making powerheads can help corals by simulating the natural back and forth movements of the ocean, yet - often times they are more for show than for function - as they do not direct the flow of detritus out of the aquarium.
---
If I have a 100g aquarium, for example, the rule of thumb states that I should have anywhere from 1000 to 2000 GPH of internal water flow going through the tank. If I buy a couple of 1200gph koralias and stick them in each corner of my tank, is it actually doing any good at all?? I don't think so.
Flow should be directed - where it has a purpose. That purpose, mainly, is to:
1. carry food to corals
2. carry waste away from corals
3. carry CO2 away from corals.
4. carry detritus into mechanical filtration
Assumptions:
1. That if there is any water movement at all, that over time a food will be diffused into the tank in equal proportions regardless of water flow patterns. (feeding liquid foods like oysterfeast.)
2. That if there is any water movement at all, gas exchange will occur, as long as pH is stable in proper proportions.
3. Waves are for human enjoyment.
4. build up of waste, detritus and mulm will occur.
So... does it really matter what flow patterns there are? SURE!
1. Gas exchange occurs best when a powerhead is placed at to blow across the tank at the water line. (with the added benefit of blowing waste into the overflow box.)
2. Oscillating patterns give corals a chance for peace in between oscillations.
3. Dead spots have to be maintained and detritus has to be removed and can be facilitated by water movement. Will all detritus be removed through water flow alone? No. This is where the aquarist has to intervene.
Does this mean that I have to have X amount of flow for X gallons of water? NO. it means that you should give your flow patterns thought before buying a powerhead. What are you trying to accomplish? Do the corals you are keeping actually need that much flow?? I don't think so. One of my most successful systems was a 55g tank with one maxijet 1200 powerhead and two aquaclear filters. WHAT?! How could this be?!?!?!?!
Give it some thought. We may be pushing tooo much flow through our tanks and not giving flow patterns enough thought.
 
acrylic51

acrylic51

Active Member
Patterns IMO would be more important.....You could have tons of flow, flowing, which really equivocates to nothing unless it's being used efficiently.....You could take 20,000gph pump and aim the return at the front glass doesn't mean your flow is effective.....
 
vettitude

vettitude

New Member
I definitely agree with what is being said.
Thanks for the well thought out and well explained article!
 
pezenfuego

pezenfuego

Active Member
Since starting this hobby I have come across dozens of these rules-of-thumb. I have yet to find one that I agree with or that has no counter-example. Maybe that should be your next article ;).
But you raise several good points and remind us that nothing in this hobby is quantifiable and that every tank and situation is different.
 
M

mikelombardo

Guest
Great post Snake, I'm working with a Sicce Voyager 1 and it has a neat feature that spins and makes for some nice motion in the tank, wel see in a month or so how the corals do, I'm thinking they're gonna love it! definitely not about pressure but about motion, Eric Borneman talks about that in his book alot! Thanks for the great post!
 
cav414

cav414

Member
Hello,
I was trying to get the info on my power heads before I made this post but they are old and have no readable markings left ( I bought my tank used).
Okay I have a 55g tank with live rock, star polyps, niger trigger, blue damsel, valentini saddle puffer, yellow tail damsel, and chocolate chip sea star. I have to power heads I think they would be considered strait flow.
Right now I have both pointed at the front glass heating what I think is a turbulent flow to help with an algae problem on my star polyps (problem was hopefully fixed as of yesterday).
My question is would this flow be good to keep or should I change it? I know the polyps don't get much of a break from the flow. I'll post a picture of my rock formation.
Thanks in advance
 
flower

flower

Well-Known Member
cav414, I'm not a big brain like most of the reef keeping folks. I set up my tank and made sure no areas had any dead spots with no flow. Some areas naturally had stronger flow then others. I used a stick with a plastic ribbon to check where the power heads created current and how strong or weak the flow to certain areas were.

When I had my reef system for 11 years, I just always made sure I had the surface water moving real well to have the best gas exchange, and I knew where the strongest water movement was for the corals who needed a strong flow, so that fact decided what corals could be placed there....and where the weakest movement was for the type of corals that like things a little more quiet. Then I factored in the light needs. I made sure any corals I purchased that needed to be hand fed were within easy reach, and the filter feeders were happy enough as long as there was food dosed in the tank. I also made sure the water parameters were the best and most stable I could manage.

All that technical stuff....of why...
for me it came down to just knowing my tank. If a coral is being beat to death by the flow in a certain area, or is so unhappy it closed up...I moved the coral to a better place. I didn't adjust my tank to accommodate the coral, rather I selected and placed corals that would be happiest in whatever open area I had available. I also concerned myself with the corals aggression, a bubble coral for example had to be down flow of other corals so the night tendrils wouldn't sting them to death. Running carbon took care of the chemical warfare the others unleashed.

Adjusting flow to accommodate corals makes no sense, you will drive yourself crazy. To combat algae, make sure to get all phosphates and nitrates out of the system. If the corals can't handle strong light and develop algae, they need a shaded area if light needs permit, or lower placement in the tank.
 
snakeblitz33

snakeblitz33

Well-Known Member
Yeah, you have what looks like something like a maxijet powerhead. They have linear flow, so your back wall isn't getting much flow, and more than likely you are going to have dead spots behind your rock work.

Since I switched over to a variable flow wide range powerhead, I can tell a major difference in the amount of flow in the tank - but not only that, the water is much clearer, since more detritus is stirred up and can enter the mechanical filtration. A great alternative to an expensive vortech or Tunze powerhead is a Jebao powerhead. I'd say to get the WP25, which should be more then plenty flow.

Take advantage of the technology available to todays aquarists. While you can still have a successful tank with outdated equipment, there are much abetter alternatives out there that are coming down in price.

I'm kind of concerned about how low your water level is... check your salinity and add either fresh or saltwater depending on what it is. You should always have your tank filled up as high as you can. The water volume helps the tank maintain stability, which is very important.
 
cav414

cav414

Member
Thank you both I definitely like the stick idea I will do that and I am going to start updating my equipment as soon as get the funds for it lol. And with the water level that picture was taken right after cleaning my rock and back glass I usually keep it up to the bottom of my hob filter.
 
flower

flower

Well-Known Member
Quote:
Originally Posted by cav414 http:///t/393291/reef-flow-rates-discussion#post_3532671
Thank you both I definitely like the stick idea I will do that and I am going to start updating my equipment as soon as get the funds for it lol. And with the water level that picture was taken right after cleaning my rock and back glass I usually keep it up to the bottom of my hob filter.

Between the folks with so much hands on know how, here on the site, and this book, it really helped me. I'm posting a page as well so you can see the info it contains...you should get it. It explains the coral, tells you what food it needs, and most important the quick stats of placement, aggression, water and light needs. Click on the picture for a larger image, so you can read the page.



 
cav414

cav414

Member
That's definitely going My list of must buys thanks. I plan on switching to a reef tank around april so I will get this book and do more research as soon as I can. I just wanna add i'm very happy I found this forum :)
 
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