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75g light/nutrient balance no CO2 question

1044 Views 8 Replies 6 Participants Last post by  GoodwillTKE
Right now on my 75g I have a solarmax t5HE (which, I asume is NO equivalent) 48" 2x 28w light set up with two 10k bulbs set in the middle of my tank. I calculated that out to be about .75 watts/gal, definately in the low light range.

I have all low-medium light plants right now, and plan to stay in that range as I do not want to fuss with CO2 this early in my experience.

Problem is I am worried about equal distribution of that low light. If I were to purchase a second of the same light fixture to put on the front edge of the tank, moving the first to the rear, and stick with the actinic that comes along with it and put in a 6,700 instead of one of the 10ks. Then I would have 4 bulbs, actinic/10k/10k/6700.

I figure that should hit me about 1.5 watts/gal, and pretty even lighting. Would this low/medium light still be low enough to avoid the need for CO2?

I assume I would need to occasionally add some light ferts into the tank occasionally. I do have flourite/gravel substrate mix, and will be adding a decent amount of fish once my tank has become stablized.

I would appriciate any advice here.

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Don't try to get the amount of light you need by looking at watts per gallon. That will most likely just mislead you. Instead, think in terms of the type of lighting, T5HO, T5NO, T8, PC, etc. Your tank is 48 x 18 x 24 (I assume), so if your lights sit on the top of the tank, they will be about 22-23 inches from the substrate. At that distance a single T5HO bulb should give you low medium light - around 50 micromols of PAR. But, the 18 inch depth of the tank precludes using just one bulb and getting uniform lighting over the substrate. One way around that is to take advantage of Catalina Aquarium's cheap customizing prices, and have them make a 2 bulb, T5HO light, using the housing normally used for a 6 bulb fixture, and having the two bulbs separated as far as they can get them - about 8 inches or so. That should give you about the same 50 micromols of PAR, but much more uniformly over the substrate.
Another option would be to get a 2nd T5NO fixture. You could then experiment with the photoperiod to "dial in" exactly what works best- running both fixtures for just a short period of time, running them in tandem...? Having 2 fixtures (4 bulbs) would also help address the 18" back-to-front tank depth issue.

If it were me I'd try running one for 8 hours a day and then adding in the 2nd for about a 4 hour "noon burst".
Thank you for the input.

I'm still trying to get a grasp on the differences in bulbs. I keep reading all the information I can find, but it is a lot to absorb. It doesn't help that my fixture calls itself HE either. I have made the assumption that that makes it equivalent to a T5NO, so as I read more about lighting I am trying to simply focus on the T5NO information.

I was considering doing something along those lines. Especially considering I have two bulbs, but only 1 power cord for the both, so I am either on or off. The second fixture would give me a way to be a bit more flexible.

Luckily my tank is in my basement hang out room, so I can make "daytime" be whenever I want it to be.

This is an excellent thread on the different types of light and "range" of light intensity. Two T5NO bulbs as in your fixture puts you around the Medium light range, adding another fixture will bump you into the High light range, I would stay away from that without CO2.

By the way, do you have any pictures of this light fixture, I was interested in this unit for a new 55 gallon I am picking up this week.
I have little trouble lighting my tank front to back with a T5HO fixture, mind you it is suspended above the tank.
After reading the PAR thread, and doing a little more research, I think I have a decent handle on lighting. I am planning on getting a second fixture, and will then probably only run 1 bulb in each for a while just to get a little better spread. Then, once I get comfortable, if I decide to upgrade to a CO2 system, I have the lighting capacity to do so.

From what I have read, the light levels drive the need for CO2 and ferts. With my tank running solidly in the medium light range, what kind of fert dosing would be appropriate given my lack of CO2 injection? Most everything about ferts I have read is geared to high light CO2, and I haven't noticed any sort of scaling factor as you gear down the lighting and remove CO2. The majority of any adjustment recommendations seem to be 'turn up the CO2 and lower the photo period' while continuing the overdose-waterchange method.

I want to make sure I am providing the right nutrients to keep my plants healthy and happy. I would assume some sort low level monthly supplimenting would be helpful.
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not sure if you decided on the T5HO fixture but on mine i can not run only 1 bulb. both have to be on or the fixture will not work. not sure if they are all like that.
I'll have 2, 2 bulb NO fixtures, but they have switches allowing me to run each of the bulbs independently. I should be able to run 0, 1, 2, 3, or 4 bulbs between the two timers and 4 switches.

If I set it up for 2 timered bulbs, I can have the option of switching 2 more on for noon burst or visual enhancement depending on the bulbs I use as I understand it.
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