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Cetus and Nexus working together - advice please

General discussion about all things Koi

Postby alpina » Tue Dec 08, 2009 6:20 am

Hi all,

I've finally worked out the gear I want and would appreciate some advice on the best way to set it up.

My pond is an above ground indoor setup (concrete and fibreglassed) with glass front holding about 4500lts.

I'm thinking BD to Cetus (gravity fed) and then pumped (sequence 10k) to Nexus 200 and then gravity fed back to pond. At inlet of the Nexus there will be a "T" and I will pump feed (sequence 6k) the skimmer in also (do I have to pump feed the skimmer?). The outlet of the nexus will flow though a 30w UV clarifier and then back into pond. Im hoping to sit the nexus about 100mm above the water line to achieve this effect ... will this work? How many returns should I use and what size?

My other option is the balanced gravity setup but this will mean another pump and I'm concerned about bacteria growing in the balanced line.

Which of the two options is best?

As I'm at the ordering stage, I'd appreciate any advice you guys can give.

Cheers.
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Postby Drulton » Tue Dec 08, 2009 2:10 pm

Page 7. [;)]. Click on the cetus manual icon.

[url=http://www.evolutionaqua.com/acatalog/The_Cetus_Sieve.html]http://www.evolutionaqua.com/acatalog/The_Cetus_Sieve.html[/url]
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Postby gibbo » Tue Dec 08, 2009 3:00 pm

Hi

Let me check I have read this right.

You will have a cetus sieve with a t'd inlet, one being fed by gravity from bottom drain and one being fed by 6000 pump from skimmer. Then 10000 pump on outlet of cetus going to nexus.

If this is correct then what will happen is the bottom drain will only pull 4000 per hour as you are only pulling 10000 out of the Cetus in total and already putting 6000 in via the skimmer pump.

A better option would be to gravity feed from skimmer and bottom drain to the cetus using a t (and balancing both inlets with valves) and then using a bigger pump on the outlet to pump through the uv and into the nexus, which then returns by gravity.

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Postby rigger1971 » Tue Dec 08, 2009 7:26 pm

no gibbo what hes saying is a t just before the nexus with a 6k pumping from the skimmer into the cetus line which is already pumping via a 10k so 16k in all of pumped water into nexus then gravity return?

i dunno if youd get that much thru a 4" pipe there wont be much head loss because of back pressure??
and i dont know about the 16k an hour gravity returning?? whats it returning thru? it,d have to be 4" minimum otherwise itll overflow!

no pond!! what do i know eh??

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Postby gibbo » Tue Dec 08, 2009 8:00 pm

Cheers rigger, well spotted.

I wouldnt take this approach, it's too much to put through the nexus 200. Also why bypass the sieve with the skimmer flow, it can easily handle the combined flow.

Plus the pond is 4500 litres so a 10000 pump will turn it over every 30 minutes or so. 16000 would be a little more than needed and perhaps waste of eleccy.

Rigger, where you say about getting that much through a 4" pipe do you mean incoming (the beginning of your second paragraph). If so its no problem. I only use 3" pipe for 12000 per hour. I can drain the 20000 litres pond empty through 1 x 3" pipe in 20 minutes. I've also had 10,000 lites pumped to a gravity return using 2 x 11/2" outlets inthe past (1 was not enough).

Personally on this size pond I would still go down the route of putting both inlets through the sieve, pump to the nexus and then gravity return. Valve both inlets so they can be balanced, and use only 1 pump. A 10,000 litre per hour would be fine, although if you wanted you could possibly consider a 12000 to take into account the UV and head to the nexus (bear in mind the head is lower than the pond level it is worked from the level of water in the base of the sieve.
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Postby rigger1971 » Tue Dec 08, 2009 8:50 pm

yes i understand that m8 i also didnt read it was only 4500 lol!!!
but to be fair its a lot to get thru a 4" by gravity without a pump speeding it up??
BUT the 10,000 would be more than adequate on its own to cover everything on a pond so small!!
and a 200 on 1000 gallons?i know theres no such thing as too much filtration but!??

no pond!! what do i know eh??

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Postby alpina » Tue Dec 08, 2009 11:03 pm

guys,

thank you so much for your help.

my original plan was to do as per page 7 on http://www.evolutionaqua.com/acatalog/The_Cetus_Sieve.html

ie, 4" aerated bd and skimmer controlled by valves into cetus, then pump (10k lts ph) to nexus, then pump (10k lts ph) to uv and pond, all the time using a balanced line. by using various valves, i could use the cetus or nexus independently or simultaneously (not that i think i ever would).

i was surprised that my dealer told me that if i have the nexus 100-150mm above water level that i would not need to pump from nexus to pond and that gravity would handle it.

given that the pond is indoor and leaves will not be an issue, what sort of flow should i allow for the skimmer?

will i need 1 or 2 tpr's and what size would they need to be?

thanks
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Postby koicarpus » Tue Dec 08, 2009 11:36 pm

Hi Mate,

I'm pretty certain you probably won't need a skimmer, and you definately won't need a cetus before your nexus 200 as your pond is indoors.
IMHO it's a waste of money, but if you cannot resist then balance pipe and two pumps, and ditch the skimmer.
The nexus 200 is more than capable of running a 1000g indoor pond, and that's all you'll need[:)]
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Postby alpina » Wed Dec 09, 2009 12:26 am

thanks dave,

thinking i'll go balanced line and use 2 pumps.

I know it's probably overkill with the cetus but it for an indoor retail environment and I don't want to take any chances with dirty water, odours, etc.

I was thinking skimmer just to pull any oils or floating food that might rest of the surface.
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Postby koicarpus » Wed Dec 09, 2009 11:50 am

Hi Mate,
Nothing wrong with overkill regarding filters, if you can afford it then why not[:)]
The balance pipe, even though you need two pumps, is easy to install, and you can have it all at water level height.
I suppose it's not that expensive to install a skimmer so it won't hurt, but i really do believe you will not need a cetus sieve, save yourself the money and buy a couple of decent koi instead.
The eazy 200 will easily filter your water to a high standard, the cetus only handles solids, as your pond will not have leaves, twigs, blanket weed, frogs etc etc it really is overkill.
Hope I've helped in some way,
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Postby gibbo » Wed Dec 09, 2009 12:23 pm

Hi

I would agree with Dave that the Cetus is potentially uneccesary as the pond is indoors. The nexus 200 will easily cope with the size of pond.

However if you are happy to spend the money then the Cetus will benefit you in that it will remove any waste from the water, and lower the maintenance on the nexus, although again you are in an indoor environment so this will be lower anyway. The Cetus also breaks up the water as it passes over the sieve which I personally think adds to the water quality.

If you go down the route of both units I would consider pumping from the cetus to nexus and then gravity flow back to the pond, i.e. raise the nexus enough to do this. It will save you the cost of buying and running a second pump. This is obviosuly if you dont mind having the top of the nexus higher than the pond.

Also please dont use 2 pumps the same size if you go down the route of the two units level with a balance pipe. You need to have the pump from the sieve lower capacity than the pump from the nexus. Trying to use 2 pumps the same size could cause all sorts of issues such as the nexus running dry or overflowing. It is far simpler to use 2 pumps. I use a 10000 from the sieve and 12000 from the nexus. This method means 2000 per hour bypasses the sieve. Some suggest running this in reverse so that the 12000 runs from the sieve and 10000 from the nexus, however I consider this a waste of power as you are recirculating 2000 per hour over the sieve

And I would put a skimmer on, especially if you want the pond to look nice and crisp on the surface in a retail environment (and you will sometimes get floating fish poo for example). As I mentioned before this could be t'd into the bottom drain inlet either to the sieve (or the nexus if you chose not use a sieve), and balanced with a valve. On this sixe pond you will not need a great pull on the skimmer, just enough to keep a small amount passing through and the surface looking nice.

Hope that makes sense
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Postby alpina » Thu Dec 10, 2009 12:20 am

Very helpful guys - thank you so much :)

Will go balanced pipe option as having the nexus outlet above pond level which is already 1.2mts above the ground will look terrible.

Thanks for the tip regarding varying the pump sizes. Shame sequence don't make a 8k/lt pump as I think an 8k (from cetus) and 10k (from nexus) would have been ideal. Really leaves me with 10k and 12k option, but aware of the significant increase in power draw of the 12k model vs the smaller units.

Any suggestions about for a good gravity fed skimmer (will "T" into cetus) that's more for polishing water surface that for picking up leaves, etc? Pics or links would be appreciated :)

Will order gear soon and will bug you all again about how best to plumb / valve it later :)

Cheers.

BTW - I hear you about the cetus being unnecessary and overkill, but will go ahead with it anyway. I only hope the result will be visually better, even if it's only marginally (although perhaps not cost effective) than not having it.
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Postby koicarpus » Thu Dec 10, 2009 12:53 am


[quote]ORIGINAL: gibbo

[b]Hi


Also please dont use 2 pumps the same size if you go down the route of the two units level with a balance pipe. You need to have the pump from the sieve lower capacity than the pump from the nexus. Trying to use 2 pumps the same size could cause all sorts of issues such as the nexus running dry or overflowing. It is far simpler to use 2 pumps. I use a 10000 from the sieve and 12000 from the nexus. This method means 2000 per hour bypasses the sieve. Some suggest running this in reverse so that the 12000 runs from the sieve and 10000 from the nexus, however I consider this a waste of power as you are recirculating 2000 per hour over the sieve[/b]

Hi Mate
I'm sorry I don't agree with this, if you are going to the expense of buying the cetus and extra pump then why would you not fully reep the awards of your expense.
You need a higher flow from the pump feeding the nexus from the cetus to make sure all water is pre-filtered. I don't understand why some people would prefer to save £100 a year on running cost and buy a smaller pump, and only pre-filter 75% of the water before it hits the nexus.
The nexus won't overflow or run dry, that's the purpose of the balance pipe.
This set-up is recommended by the people who designed it, it works very well for me and other people, make sure you have a higher flow from cetus to nexus than nexus to pond, just to make sure you have pre-filtered all pond water, do it right, do it once[:)]
Dave

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Postby alpina » Thu Dec 10, 2009 1:10 am

Damn, trust it all to get confusing again.

Ok, so maximum flow rate of 200 is 10k lts/hr.

My original thought was to just use 2 * sequence 10k pumps but then there was some concern that that pumps should not be equally rated. Can I just go this way (ie, 2* 10k) or is the general consensus that I go 12k from cetus and 10k from pond. I want to use sequence pumps.

sorry to get bogged down on this pt :(

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Postby koicarpus » Thu Dec 10, 2009 1:26 am

Hi mate,
It's difficult to say, the return from your nexus will probably have more restrictions, i.e. u.v. heater, and underwater return, therefore you will not be getting the actual 10,000lph that the pump is rated at.
With pumps it is very much 'suck it and see'. maybe if you use the same rated pumps you may achieve the higher flow from cetus to nexus because of this reason.
It's not the end of the world if you don't fully achieve this, it's pretty impossible to meaure the flow of both pumps to make sure if you've achieved it or not.
Try and calculate head loss etc for the pumps, not easy I know,
good luck.
Dave
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Postby alpina » Thu Dec 10, 2009 1:26 am

lol,

head spin for sure :)

btw, sequence 10k draws 95w and 12k draws 210w. cost price difference of the 2 is marginal (less than $AUS100) between them.

plan to set the cetus and nexus with valves in a way that i can totally isolate them in the event of 1 failing (will only do this in this event).

nexus will pump all water into a 30w UV clarifier and come out into pond via 2 tpr's (probably 1.5 or 2" each). good option regarding quantity and size of tpr's?

can go 12k as long as it doesn't overload anything. I can see the benefit of overfiltering into cetus thanks to balanced line workings :)

Really learning a lot here :)
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Postby koicarpus » Thu Dec 10, 2009 1:43 am

I wish you all the very best, sounds like your having fun,
keep us posted with plenty of pictures.
Kind Regards
Dave
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Postby gibbo » Thu Dec 10, 2009 11:43 am

OK, I think maybe I have been one sided in my previous posts and not acknowledged there are two methods to do this. For easy comparison lets look at both options and use the same pumps in both, a sequence 10,000 and a sequence 12000. For simplicity lets assume they are both operating at the stated flow rate.

Option 1.

The original design which is to put the larger pump on the Cetus outlet and the smaller pump on the Nexus outlet. The balance pipe in this case is on the outlet of the nexus to the inlet of the Cetus, allowing any excess water to be returned to the Cetus preventing the Nexus overflowing.

In this scenario more water is being pumped into the Nexus than being returned to the pond, therefore some of it is returned to the Cetus.

So 12000 litres per hour is drawn through the Cetus, and then pumped into the Nexus. Only 10000 litres per hour is returned to the pond. Therefore 2000 litres per hour is continually circulated through the Cetus and Nexus, providing no benefit, as it has already been through the system once. 10000 litres is being taken from the pond per hour, filtered and returned.

However the plus side of this is that all the water is prefiltered through the Cetus.

Option 2.

My design which I implemented and run, which is to put the smaller pump on the Cetus outlet and the larger pump on the Nexus outlet. The balance pipe in this case is from the bottom drain line to the Nexus inlet, allowing any additional water required to match the flow of the Nexus outlet pump to be drawn directly from the bottom drain.

In this scenarion more water is being pumped from the Nexus than is being pumped in from the Cetus and therefore some is drawn directly from the bottom drain.

So 10000 litres per hour is being drawn through the Cetus, and then pumped into the Nexus. An additional 2000 litres per hour (which I think is 16% not 25%), is drawn into the Nexus directly from the bottom drain. No water is continually circulated through the filtration, all is passed through once and returned to the pond. 12000 litres per hour is being taken form the pond, filtered and returned.

However the down side of this is that 16% of the water is not filtered by the Cetus. One observation I have made though is the waste seems to flow through to the Cetus as it follows the greater flow, i.e. there is a 10000 lph pull to the Cetus and a 2000 lph pull to the Nexus, so it tends to follow the greater pull.


So by using option 2, 20% more water per hour is being filtered using exactly the same pumps and energy. The Eazy element of the Nexus is being asked to handle only 2000 litres per hour which it can handle with ease, and is a fraction of its capability.


Some further advice I would add.

1. Always fit a non return valve on the exit of a Cetus, to prevent water backflowing into it if you turn the pump off. I found the best place is directly on the outlet, before the pump. In trials I found if the valve is placed after the pump you can sometimes get an airlock when you turn the pump off making it difficult to restart the circulation.

2. Put the UV, Heater etc on the Nexus outlet. This allows you to turn the Cetus off (as I do in winter) without affecting these units. On my setup I just turn the pump off from the Cetus and thats it (the non return valve is important here). The Cetus is bypassed and the Nexus continues to circulate using its own pump. Also if option 2 is chosen then the restrictions incurred by the UV etc are on the higher powered pump, and are actually reducing it nearer to the speed of the smaller pump, further reducing the amount of water pulled through the balance pipe. If option 1 is chosen the restrictions are actually placed on the smaller pump, thereby increasing the amount of water which is continually recirculated through the filtration system.


For these reasons my own preference is option 2. Hopefully by explaining this above people can form their own opinions and implement it in the way the condsider best, as both will work.


Regarding the Sequence pumps I'm getting confused by some of the points mentioned (bearing in mind I sell them) Sequence do make a 8000 pump, they also make a 10,000 and a 12000, as well as larger units.

The sequence 8000 is rated at 72-83 watts
The sequence 10000 is rated at 72-87 watts
The sequence 12000 is rated at 72-92 watts (not sure where 210 watts comes from)

So as you can see the power consumption is very similar across the three. I believe to 12000 is the best value for money both from a purchase price/performance and a running cost/performance.

But its important to size these right. And I would definately not use 2 pumps of the same size. Using either option 1 or 2 I would still use 1 pump slightly larger than the other.

I use myself, and would recommend a 10000 and 12000 on a 300 setup.
Perhaps an 8000 and 10000 would be more suited to a 200 setup.


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Postby alpina » Thu Dec 10, 2009 1:56 pm

Hi Gibbo,

Thank you for the detailed explanation, all of which made sense to me :)

As for the pump size and ratings, I got them from the australian nexus supplier website. From what I can tell after talking to 2 retailers, the 8k lts/hr models in not available here.

Sorry to trouble you a step further but do you by any chance have a diagram of how you have set up your system including valves (non returns included), etc? I for one would find it very helpful as I'm not 100% sure how the balanced line is working.

I didn't realise it was a simple matter of just turning off the cetus pump to bypass it? is is also the case that if I was to turn off the nexus pump instead that all the flow would run through the cetus only and back to the pond?

I'm assuming of course that a 4" BD can handle a flow far greater than 12k lts/hr?

Finally, do you see any problem with me running an 8k and 10k pump on the nexus 200 and cetus?

Cheers.
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Postby gibbo » Thu Dec 10, 2009 3:36 pm

Hi, no problem. Here is a diagram I have just drawn up which I hope makes sense ?

Unfortunately without modifying the pipework you cannot just turn off the Nexus pump and leave the sieve running as the Nexus would overflow. But yes to isolate the sieve just turn it off and the nexus will draw all its water from the balance pipe.

I also use 3" pipework which provides more than enough flow in my situation. 4" can handle way more than 12000 lph.

I have to be honest and say that I have never set this up using a nexus 200, only 300 and I always recommend 10000lph and 12000lph pumps in this scenario. I see now reason that an 8000 and 10000 would not be adequate, and actually have reservations that a 12000 on the end of your Nexus 200 would be too powerful.


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