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Discussion: Are we obsessed with circulation and flow?

George Farmer

Founder
UKAPS Team
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Cambridgeshire
The 10x turnover rule is now pretty much the expected standard for a UK medium-high energy planted tank. Others go as high as 20x or even 30x+ turnover.

So if you have a 120 litre aquarium, you need to filter it with a 1200lph filter.

If you have a 400 litre aquarium you may wish to use 2 x 1200lph filters with a powerhead to boost flow up to 4000lph minimum.

I don't think many will argue that circulation is important in the planted aquarium, especially in higher energy set-ups where the CO2 needs to be distributed effectively to reach all over the water column.

If there are dead spots then we likely suffer. The CO2 cannot reach the plant, resulting in algae. If we push up the CO2 to compensate then we risk CO2 toxicity.

So how do other hobbyists (mainly from abroad) seem to get by perfectly fine with much lower levels of circulation, yet have very high lighting levels. Some dose nutrients very lean too, and their tanks seem to flourish.

When I was compiling the Great Planted Tanks series for PFK a couple of years ago I was amazed by some of the tank specs. One claimed to have low lighting with around 1 watt per little in a 200 litre tank! Yet there was only around 3x turnover, and minimal water changes, and low nutrient dosing.

I have seen many other similar examples.

When UKAPS visited Tropica many of their tanks were filtered with one relatively small external with visibly low levels of circulation, they only dosed TPN+ on occasion, usually using TPN, yet had high lighting levels and the plants were the healthiest you've ever seen, with no signs of algae.

Even Amano's tanks aren't hugely over filtered.

So are we a tad obsessed with circulation levels, I wonder?

Please discuss! :)
 
I think we are, but ideally to understand we'd need to see the whole picture, especially when the results are so much different to our own. We often state WPG but it means nothing it's the par that's vital, maybe they're a much lower par than we think/expect. Turnover is similar, I've known a 1200lph filter to produce 450lph actually turnover once lilys and a inline heater on. I see it as redundancy by adding huge filters with loads of flow and the results can't be denied. To understand how other people get their results I think we'd need to know why algae isn't getting a hold and why the dosing can be so low compared to their lighting. It'd be interesting considering that most of us add ferts daily to see what the plants are doing to maintain health, where they're getting the nutrients from, co2 etc.

If we assume light is the driving force then we can only assume that if everything is healthy that the light levels aren't as high as we thought, even at 1wpl, the methodology of lower dosing might be something worthy of study, we know high levels don't induce algae, but what levels are the lowest eb that can still be successful. can co2 levels be the key to lower dosing, and if uptake is more than what's going in where is it coming from?

A short answer would be we yes, I think some of us are, but when compared to nature our tanks have next to no flow, even a quiet slow moving river the plants are noticeably bent in the flow.
 
Yes, it was originally, it was in the first instance 5x, people soon realised that filters were only half as powerful as stated and this was upped to 10x to give actual 5x turnover. Plus it allowed for us to have redundancy in flow rates, we soon noticed out plants liked more flow and so the flow rates kept on increasing.
 
I don't think we differentiate between circulation and filter flow enough. They are really two separate subjects.

Filter Flow = A balance based on flow rate vs volume of bio media.

Circulation = Everything should be gently swaying or above.

R

P.S. I guess the reason I think like this is because I am a firm believer in having a separate powerhead to get the current really moving, but not everyone likes the extra equipment.
 
I seem to think the 10x rule originated from a converstation between ceg and jimbo and jamesc. It was definitely in the early days of ukaps because I remember reading it all and everyone being put out that filters weren't giving the flow they quoted.
I'd dread to be a social anthropologist, I'm terrible at collating the past!
 
rufus_blackwell said:
I don't think we differentiate between circulation and filter flow enough. They are really two separate subjects.

Filter Flow = A balance based on flow rate vs volume of bio media.

Circulation = Everything should be gently swaying or above.

R

P.S. I guess the reason I think like this is because I am a firm believer in having a separate powerhead to get the current really moving, but not everyone likes the extra equipment.
Yeah, I think I'd rather an extra inlet and outlet for a second large canister filter over a powerhead though. The added media is a bonus, plus you're adding to the overall water volume.
 
JamesM said:
Oooh, still not convinced about the glassware thing :eek:
I think you misunderstand me a little, James.

I mean the visual contrast of seeing a big black powerhead in the same tank as nice glassware. May as well go the whole hog and use indestructible and easy-to-maintain plastic outlets/inlets.
 
Is it not also a lot to do with stocking? Many of the stunning tanks I've seen massively UNDER stock their tanks. Certainly as far as algae is concerned I find its more about limiting potential sources of pollution than anything else. I think (and we've all done it!) its just to tempting not to push the stocking to the limit, at which point no matter what the flow or filter or even plants the algae it getting what it needs to germinate and then no matter how well the plants are growing algae starts to take over.

Sam

EDIT - forgot to add to the over, in understocking you can reduce flow. However when you stock to the limit you need the a fast filter to remove NH3 and NO2 quickly. The 10x flow 'rule' recommended on the base of nutrient distribution, actually masts what it is really doing which is pollution removal.

If it wasn't for the high fish loading we could probably get away with much reduced flow rates.

EDIT 2 - I actually think to much flow can be detrimental.
 
George Farmer said:
Themuleous said:
I think (and we've all done it!) its just to tempting not to push the stocking to the limit,
I disagree. I've never got anywhere near overstocking a planted tank.

Yes but you have achieve good results, for people who struggle it is easy to forget stocking levels.

Sam
 
George Farmer said:
JamesM said:
Oooh, still not convinced about the glassware thing :eek:
I think you misunderstand me a little, James.

I mean the visual contrast of seeing a big black powerhead in the same tank as nice glassware. May as well go the whole hog and use indestructible and easy-to-maintain plastic outlets/inlets.

Oh right, yeah.. I agree about Korolia's too.. not a fan of them.
 
I certainly am obsessed with flow, unless I can see the plants swaying to what I think is enough I will increase. Although I started my 60l with the stock 300lph(approx) internal filter for flow, I have soon added a koralia nano(900lph), the more flow the better-to a certain extent :rolleyes: The staghorn algae is keeping at bay on my crypts now :)

Adam
 
I'm going off glassware in design, but I appreciate it's aesthetic quality. I hate Koralias, I know they're there for a purpose but I could never justify one in my tank.
 
I cant remember who started the flow discussions it possibly was James and ceg, I do remember George and Dan talking about 10X flow rates thats where I picked up on that idea first of all. Good point on flow and circulation, its about having good circulation. Having a single point source for flow in a large tank will not provide good circulation more than likely.

Koralias are ugly thats for sure, although the new nanos are a good compromise, small and quiet , but not much good in a large tank unless you use two or more so back to the ugly part again.
 
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