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120p Chihiros Selection; 1x120cm vs 2x60cm vs 1x90cm

So pardon the long introduction, but what sized light would you go for?

  • 2x60cm buddy. That will look nice, it's cheaper and it will give you enough power!

    Votes: 0 0.0%
  • 1x120cm please, it's basically the only choice.

    Votes: 3 75.0%
  • 1x90cm is indeed fine, as Balasz indicates. I have that myself and am very happy.

    Votes: 1 25.0%

  • Total voters
    4

StiekIsOnIt

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Nijmegen
Hi!
My name is Robin. I am from the Netherlands. Obviously the ukaps forum has been a welcome resource over the past years. I read and searched a lot on the ukaps forum, but couldn't find a suitable answer to my specific question. So I decided to register and ask it here, hoping it would bring me to a definitive conclusion.
To be honest, I've polled this on the r/PlantedTank reddit for the 120cm vs 90cm, which got me a 11 vs 9 voting result. Not significant if you ask me. Well, it makes me Google endlessly!

My tank
I own a rimless 120x40x50 tank. I don't have a light for this tank, but Chihiros as a brand has caught my fancy.

What size light(s)?
Balasz Farkas from green aqua indicates that a 90cm fixture is enough for a 120p tank at around 7:50 in this video ([link]https://youtu.be/7kOSrg_smy8[/link]). I tend to take his advice on ANYTHING. But with a long lasting purchase like an LED light, I wanted some more opinions, which eventually led me here. I'd love your opinions if you have time!

Chihiros
1614716855785.png

So I was looking to get a Chihiros WRGB II, of which the 90cm one is readily available to me, but the 120cm is not. The 60cm is also readily available, but I am unable to imagine if that would look bad, since 2x60 equals the width if the tank.

I will be suspending the light above the tank. Either from the roof or with a system.

The moneys?
2x60cm goes for 2x€165=€330
1x90cm would be about €240,
while the annoying 120cm would need to be imported from further away so estimating import tax and such fun would mean
1x120cm would be about €450.

Budget?
I have a max budget of 400 euros for a new light. So dual Solar RGB is not an option if you're wondering 🤗, and sadly that also excludes the Vivid 2.

WDYT?
 
Last edited:

Diogo Sousa

Member
Joined
23 Jul 2017
Messages
112
Location
SE London
Welcome!
A full length light fixture would give the sides and corners of your tank plenty of light. A shorter light fixture wouldn't but in my opinion looks nicer suspended.
So I'd say it's up to you and what kind of scapes you're planning to keep.

In my opinion 2x 60cm would just look odd.
 

oreo57

Member
Joined
19 Jun 2020
Messages
182
Location
USA
Welcome!
A full length light fixture would give the sides and corners of your tank plenty of light. A shorter light fixture wouldn't but in my opinion looks nicer suspended.
So I'd say it's up to you and what kind of scapes you're planning to keep.

In my opinion 2x 60cm would just look odd.
Hi!
My name is Robin. I am from the Netherlands. Obviously the ukaps forum has been a welcome resource over the past years. I read and searched a lot on the ukaps forum, but couldn't find a suitable answer to my specific question. So I decided to register and ask it here, hoping it would bring me to a definitive conclusion.
To be honest, I've polled this on the r/PlantedTank reddit for the 120cm vs 90cm, which got me a 11 vs 9 voting result. Not significant if you ask me. Well, it makes me Google endlessly!

My tank
I own a rimless 120x40x50 tank. I don't have a light for this tank, but Chihiros as a brand has caught my fancy.

What size light(s)?
Balasz Farkas from green aqua indicates that a 90cm fixture is enough for a 120p tank at around 7:50 in this video ([link]https://youtu.be/7kOSrg_smy8[/link]). I tend to take his advice on ANYTHING. But with a long lasting purchase like an LED light, I wanted some more opinions, which eventually led me here. I'd love your opinions if you have time!

Chihiros
View attachment 164047

So I was looking to get a Chihiros WRGB II, of which the 90cm one is readily available to me, but the 120cm is not. The 60cm is also readily available, but I am unable to imagine if that would look bad, since 2x60 equals the width if the tank.

I will be suspending the light above the tank. Either from the roof or with a system.

The moneys?
2x60cm goes for 2x€165=€330
1x90cm would be about €240,
while the annoying 120cm would need to be imported from further away so estimating import tax and such fun would mean
1x120cm would be about €450.

Budget?
I have a max budget of 400 euros for a new light. So dual Solar RGB is not an option if you're wondering 🤗, and sadly that also excludes the Vivid 2.

WDYT?
First thing is are you going to suspend it higher than the normal mounting height?

See if you can find these:
Amazon product
 

Wookii

Member
Joined
13 Nov 2019
Messages
1,739
Location
Nottingham
The 120cm light will give you the best coverage of course, but a 90cm light may be sufficient, as its only 150mm at each end of the tank - as long as you don't place demanding plants at the ends, you should be fine. The WGRB II is a fairly bright light, but due to the inverse square law relationship between the light intensity and distance, you can't raise it too far above the tank.

If it weren't for your budget restriction though, my default advice would be 2 x Vivid II's which would allow you to suspend the lights much higher due to their output power, and it makes for nicer viewing of the tank from above, and much easier access for maintenance.
 

Zeus.

Fertz Calc Meister
Joined
1 Oct 2016
Messages
3,856
Location
Yorkshire,UK
If it weren't for your budget restriction though,

ADA RGB solar are very very nice, shame you cant control the intensity via controller, for the price you should get an ADA agent to come round and switch them on/off for the first year at least :rolleyes:
 

Wookii

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13 Nov 2019
Messages
1,739
Location
Nottingham
ADA RGB solar are very very nice, shame you cant control the intensity via controller, for the price you should get an ADA agent to come round and switch them on/off for the first year at least :rolleyes:

Agreed. I'm hesitant to comment given I haven't seen ADA Solar RGB's in person, but their published spectrum looks to be identical to the Chihiros one, so I'd wager they use the exact same LED's. Given you have complete control over the spectrum, the individual red, green and blue output, and daily intensity scheduling of each channel on the Chihiros app, I really struggle to see a compelling reason to consider the ADA version.
 

Zeus.

Fertz Calc Meister
Joined
1 Oct 2016
Messages
3,856
Location
Yorkshire,UK
Having seen the ADA solar RGBs at Green Aqua they are the 'DB's' or would be 'if' intensity was controllable, I was very impressed with the specs/vids on the Chihiros when I checked them out some time back. If I was buying I would be looking at them seriously as my present 'dated' Chihiros LED lights was great value for money IMO and easy to control with cheap TC420
 

StiekIsOnIt

New Member
Thread starter
Joined
2 Mar 2021
Messages
8
Location
Nijmegen
Welcome!
A full length light fixture would give the sides and corners of your tank plenty of light. A shorter light fixture wouldn't but in my opinion looks nicer suspended.
So I'd say it's up to you and what kind of scapes you're planning to keep.

In my opinion 2x 60cm would just look odd.
Ok! Agreed, you confirmed the odd look of the 2x60cm.
I am looking to go for a wild scape with a lot of hardscape. Most demanding plants will probably be Alternanthera Reineckii, Hygrophila Pinnatifida, but I do want bushy Rotala that turn red.
Now while those won't be on the sides, it would be a shame if I regret the lights in the long run.
First thing is are you going to suspend it higher than the normal mounting height?

See if you can find these:
Amazon product
Well, depends on what you call normal mounting height. They will be higher than they would be with the brackets they come with. But I think I'll just be going for Chihiros brackets tbh. But I think the link is not for the brackets but for the lights? I don't think I'll go for those, but thanks for the tip!

The 120cm light will give you the best coverage of course, but a 90cm light may be sufficient, as its only 150mm at each end of the tank - as long as you don't place demanding plants at the ends, you should be fine. The WGRB II is a fairly bright light, but due to the inverse square law relationship between the light intensity and distance, you can't raise it too far above the tank.

If it weren't for your budget restriction though, my default advice would be 2 x Vivid II's which would allow you to suspend the lights much higher due to their output power, and it makes for nicer viewing of the tank from above, and much easier access for maintenance.
I am looking to usu the brackets from Chihiros, for which I found these dimensions;
1614776681730.png
<<<< these, would have me end up at ~30 cm above the tank I think.
So not too high. (right?)
And yes, I would love the Vivid 2's, but I need to draw the line somewhere. Also need a second filter and a ton of wood.

:)
 

Wookii

Member
Joined
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Messages
1,739
Location
Nottingham
Ok! Agreed, you confirmed the odd look of the 2x60cm.
I am looking to go for a wild scape with a lot of hardscape. Most demanding plants will probably be Alternanthera Reineckii, Hygrophila Pinnatifida, but I do want bushy Rotala that turn red.
Now while those won't be on the sides, it would be a shame if I regret the lights in the long run.

Well, depends on what you call normal mounting height. They will be higher than they would be with the brackets they come with. But I think I'll just be going for Chihiros brackets tbh. But I think the link is not for the brackets but for the lights? I don't think I'll go for those, but thanks for the tip!


I am looking to usu the brackets from Chihiros, for which I found these dimensions;
View attachment 164072<<<< these, would have me end up at ~30 cm above the tank I think.
So not too high. (right?)
And yes, I would love the Vivid 2's, but I need to draw the line somewhere. Also need a second filter and a ton of wood.

:)

I think the standard WRGB II legs put the light at around 100-150mm off the tank rim. Given your tank is 500mm deep, and if we assume say 50mm of substrate, using the supports you pictured above instead will increase the distance to substrate from 550/600mm to 750mm. if my inverse square law calculations are correct, that would result in a 35-45% reduction in light intensity at the substrate.
 

StiekIsOnIt

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Thread starter
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I think the standard WRGB II legs put the light at around 100-150mm off the tank rim. Given your tank is 500mm deep, and if we assume say 50mm of substrate, using the supports you pictured above instead will increase the distance to substrate from 550/600mm to 750mm. if my inverse square law calculations are correct, that would result in a 35-45% reduction in light intensity at the substrate.
I did not know that law.
The example woud be with double distance.;
If we take
600mm = 1r,
1200mm = 2r,
We take 2^2=4. Intensity/4, means 25% of the intensity at double distance. So that works.

My situation would be at best
550 = r, 750=1.364r, 1.364^2=1.86, Intensity/1.86 is .538%. 46.2% loss.
600 = r, 750=1.25r, 1.25^2=1.563, Intensity/1.563 is .64%. 36% loss.

So yea! Nice calcs there!

That seems valid for all suspension systems obviously. I'm assuming the WRGBII still has enough power when at 100%, but might be stretching is. I would want to suspend the 120cm one as well tbh, would you advise against that Wookii?
 

StiekIsOnIt

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Here still thinking to get a twinstar.
In the search for information i found these 2 videos (first one to see the difference between the II and III versions)

And another comparison:
I believe he's making a Twinstart III vs Chihiros WRGBII video as well. :)
 

Wookii

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Nottingham
I did not know that law.
The example woud be with double distance.;
If we take
600mm = 1r,
1200mm = 2r,
We take 2^2=4. Intensity/4, means 25% of the intensity at double distance. So that works.

My situation would be at best
550 = r, 750=1.364r, 1.364^2=1.86, Intensity/1.86 is .538%. 46.2% loss.
600 = r, 750=1.25r, 1.25^2=1.563, Intensity/1.563 is .64%. 36% loss.

So yea! Nice calcs there!

That seems valid for all suspension systems obviously. I'm assuming the WRGBII still has enough power when at 100%, but might be stretching is. I would want to suspend the 120cm one as well tbh, would you advise against that Wookii?

It's hard to say to be honest. The WRGB II's do put out a lot of light. If you accept that Chihiros's PAR diagrams to be accurate:

1614783272012.png


Then on your 400mm wide tank you're looking at between 90-120 PAR at 550mm depth (not clear whether that's through water or air). With your 46.2% loss, you'll be down to around 48-65 PAR. As I say, it could be lower if Chihiros's measurements are actually in air rather than water, but then you'll also get some reflection off the glass which will give some increase.

It will come down to what plants your want to grow, and only a dense carpet plant might the sufficiency of the light to the test - though again, CO2 might be more important in that case. My gut feeling is you'll be fine, particularly with the 1200mm unit.
 

StiekIsOnIt

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Sidenote; I was thinking of asking my wife for some more pocket money to get 2 Vivid II's, but decided against it. The new Biomaster 600T, a buttload of hardscape, a 120cm WRGBII; I'll be good to go for the foreseeable future. I'll keep my 400 euro budgetary limit for lights in place :)

@Wookii I did some more calculations, but I was not entirely about them.
I just used Pythagoras to calculate the diagonal to the edge of the tank, which would net another 3.5 percent loss. But as said, its not fair, since LED is very directional so you'll lose much more in the fat corners. I could not find a reliable function for dissipation of intensity from the center of the LED.

But then I looked back at your post and saw that image;
Schermafbeelding 2021-03-05 om 09.44.45.png

So at -15xm,-15cm you'll find a value of ~95.
R
1​
1,364​
^2 =
1,86​
=
53,78%​
CM
550​
750​
So this, would roughly end you up with a value of 51 given the manufacturers graphs. Well, we can substract a bit more, but that better still better than I expected.
In any case, your comment is valid, I don't suspect any problems with the 120cm. I actually think it would be the perfect fit for a 120cm tank 😉.

But then in came @Paulus with that video. Quick post there! That was a cool video. Tommy actually talks about putting a 90cm light on a 120p from 20:00. I think he verbalises what we've calculated. The corners get darker, can add to the drama of the build, and it can be something you might be looking for. My interpretation of that though, is that while getting a smaller light can add something to certain specific builds, it must be missing something for most other builds. So it is a less flexible setup.


Together with our calculations, I've reached a decision;

I'm getting a 120cm light. I think I'll enjoy the flexibility more and TBH, it will give my tank a better look.
I will use it for a number of years and I don't want to be limited by it.

Thanks for all your help guys! Cheers.
 

Wookii

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@Wookii I did some more calculations, but I was not entirely about them.
I just used Pythagoras to calculate the diagonal to the edge of the tank, which would net another 3.5 percent loss. But as said, its not fair, since LED is very directional so you'll lose much more in the fat corners. I could not find a reliable function for dissipation of intensity from the center of the LED.

But then I looked back at your post and saw that image;
View attachment 164184
So at -15xm,-15cm you'll find a value of ~95.
R
1​
1,364​
^2 =
1,86​
=
53,78%​
CM
550​
750​
So this, would roughly end you up with a value of 51 given the manufacturers graphs. Well, we can substract a bit more, but that better still better than I expected.
In any case, your comment is valid, I don't suspect any problems with the 120cm. I actually think it would be the perfect fit for a 120cm tank 😉.

But then in came @Paulus with that video. Quick post there! That was a cool video. Tommy actually talks about putting a 90cm light on a 120p from 20:00. I think he verbalises what we've calculated. The corners get darker, can add to the drama of the build, and it can be something you might be looking for. My interpretation of that though, is that while getting a smaller light can add something to certain specific builds, it must be missing something for most other builds. So it is a less flexible setup.


Together with our calculations, I've reached a decision;

I'm getting a 120cm light. I think I'll enjoy the flexibility more and TBH, it will give my tank a better look.
I will use it for a number of years and I don't want to be limited by it.

Thanks for all your help guys! Cheers.

Yeah, I wouldn't sweat the numbers too much, I think you're making the right decision going with the 1200mm.

If you want to increase the light hitting the substrate (and also reduce the light spill outside the tank), you can add some reflectors to the edges of the light. I wouldn't use the Chihiros ones, as they will be too wide an angle for your proposed light height, but you can knock up some custom ones with a a mirror polished interior and that will effectively narrow the light beam and mitigated the inverse square losses.
 

Johnwaz42

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23 Oct 2020
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I’m in the UK, can you recommend a good site to purchase either chihiros or twinstar lights please. My tank is 50cm deep running Co2 any other thoughts useful. Thank you
 

StiekIsOnIt

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I think you're a bit screwed with taxes?
You need to import the light from Asia, basically. So VAT and stuff is an issue. They have the lights on Aliexpress for cheap shipping from Spain or Poland. You then dodge any additional VAT, but I don't think thats true for you because of Brexit. Soooo, I wouldn't know buddy.
 

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