# Lighting for 90g planted tank



## funkman262 (Oct 2, 2010)

I recently upgraded from a 45g to a 90g tank. I pretty much took everything out of the 45g to put in the 90g. The only difference is that I used soil in the 90g to make it more of a Walstad type tank. The only issue I have is deciding on what lights to upgrade to for this type of tank. In my 45g, I was using 78W HO T5 which were growing my plants quite well (anubias, amazon sword, rotala indica and ambulia) and the 45 and 90 are both the same height. Would my current lights be ok for growing the same plants in the larger tank? I was thinking about upgrading to a 4-bulb T5 setup totalling 216W. With those lights, would I be able to grow higher light demanding plants without needing to dose CO2? Any advice is appreciated. Thank you.


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## davemonkey (Mar 29, 2008)

With t5HO, about 90 - 135 watts will get you where you were with the 45. More lights than that and you'll likely have to supplement one nutrient or several (you'd just have to watch for defficiencies). I think that with 216 watts t-5HO on a 90 gal, you'd need to dose CO2, at least DIY. If you went with a less efficient reflector/bulbs (PC bulbs or normal flourescent fixtures) then it probably wouldn't hurt.


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## funkman262 (Oct 2, 2010)

davemonkey said:


> With t5HO, about 90 - 135 watts will get you where you were with the 45.


The lights I currently have ARE T5HO so why would just a few more watts be equivalent on a tank double the size? Sorry, I'm still naive with lighting.

Would a 108W T5HO fixture (2 bulbs instead of 4) be fine for a 90g if I only use low-light plants?

Thanks.


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## Cichlid Junkie (Mar 25, 2005)

There is a great write up here on lighting types and depths of tanks. I refer back to it often.

http://www.plantedtank.net/forums/lighting/105774-par-vs-distance-t5-t12-pc.html


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## Seattle_Aquarist (Mar 7, 2008)

Hi funkman262,

Cichlid Junkie is correct, the link he provided contains a lot of great information. I am working on a 75 gallon "project tank" that is 24" deep, the same depth as a lot of 90 gallon aquariums. It can be difficult to get good light intensity to that depth so plants don't lose their lower leaves.

My tank has a canopy so I have the option of putting together a DIY light system and mounting it on the underside. I am looking at putting together the ballast, endcaps, standoffs, and reflectors. Here is a good article on Tek II verses Icecap SLR reflectors with quantitative PAR readings.


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## funkman262 (Oct 2, 2010)

So based on the graph, 1 T5HO bulb 24" above the soil would be on the border of low and medium light, right? And if I used 2 bulbs, it would push me to the high light range? So, considering I don't want to dose additional CO2, I should only use the 2 bulb, 108W T5HO fixture?


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## Seattle_Aquarist (Mar 7, 2008)

Hi Hi funkman262,

I've read Hoppy's post as well. In theory if your two tanks are the same depth a two bulb fixture on your 90 gallon would be the same intensity as the 2 bulb configuration on the 45 gallon (assuming the same NO or HO type bulbs).

Trying to use your old fixture on the 90 gallon would probably only give you sufficient light under the fixture area, the sides and corners would be much lower intensity.


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## funkman262 (Oct 2, 2010)

OK, I _think_ I'm starting to understand now. Since the tank is 18" wide, what I'm thinking is that I should get the 48" 108W T5HO fixture, put it in the back of the tank, and use my current 36" fixture in the front of the tank in order to get a better spread. I have driftwood across the middle of the tank so having the fixture directly above it won't do me very good. Does this make sense? Thanks.


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## Seattle_Aquarist (Mar 7, 2008)

Hi funkman262,

I think that is a good plan. In fact, you might try using just the 48" 108W and only add the 36" if the plants show signs of needing extra light.


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## funkman262 (Oct 2, 2010)

Thank you Seattle Aquarist and others. I'm going to order the fixture now and start looking for more plants to add. With these lights, would I still be very limited with my choice of plants considering I won't be dosing CO2? I'm assuming I wouldn't be able to grow any carpeting plants like grass varieties or HC. Any suggestions on easy to grow plants?


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## Seattle_Aquarist (Mar 7, 2008)

Hi funkman262,

HC likes CO2 and higher light levels. I have a 45 tall with 96 watts of AHS PC and was able to grow Echinodorus tenellus and M. minuta would work but I do have CO2.


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## funkman262 (Oct 2, 2010)

Last question: I've looked through a bunch of threads in this section but was unable to find much information on flow in a walstad tank. I was thinking about getting the Koralia Evolution 750 but I don't know if that might be too much for my tank. I was also thinking if I do the MJ1200, I could connect the airline to it for diffusion if I decide to use a DIY CO2 system (which I've already got from my 45g). Any suggestions? Thanks.


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## Seattle_Aquarist (Mar 7, 2008)

Hi funkman262,

Not really an area I am familiar with; I will leave flow comments to others. Keep us posted how things progress!


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## funkman262 (Oct 2, 2010)

Thank you again! You've been a great help  I'll create a new thread for the flow question. I'll start taking pictures and show the progression later on.


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