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T8 18W - Fluval 125

B

belly259

Member
Joined
27 Jun 2012
Messages
95
Hi all running T8 18w 2 bulbs on my Fluval 125.

Co2 injection 1.5hour before lights and off 1 hour before lights out. Lights currently on for 6 hours.
Also using dry ferts,and also dosing easy carb.

Question is do i have enough light or too much light, ? currently low/med planted due to being new to the aquarium plant/co2 workd.

Kind Regards
John
 
Yes mate, you have enough light. Having enough light should be the least of your concerns right now. You may find it bizarre, but CO2 injected tank almost always suffer from CO2 related problems, and that's because the people running those tanks always seem to think that they don't have enough light. It has been estimated that 95% of all the problems in CO2 injected tanks are CO2 related.

You are encouraged to buck this trend by ignoring your lighting and worry much much more about
A. How you will inject the CO2 effectively
B. How much flow rate your filters are providing
C. How well you are distributing that flow and CO2

Getting your CO2 and flow right means that you can actually use even less light if you wanted to. That's how important CO2 is. Stop worrying about light.

Cheers,
 
Spray bar currently attached to inlet on Fluval 305.

Im thinking Powerhead with spray bar attached to powerhead, co2 diffuser directly underneath, this would give good distribution, only question anyone know good powerhead that will attach easy to fluval spray bar kit ?
 
I'm really not sure, but it might be an easier solution to simply port the gas directly into the filter intake. I don't know the filter specifications but you might want to ensure that you are following the 10X rule. I guess this is a 125L tank? If so then 1250 LPH is the target flow rate.

Cheers,
 
Getting your CO2 and flow right means that you can actually use even less light if you wanted to. That's how important CO2 is. Stop worrying about light.
Click to expand...

Hi Clive - without appearing to be hooked in to the Matrix too much - I would be interested to know from your experience, given the above quote, what sort of intensity and duration of T8 lighting works well. I know it's not quite that simplistic, but just as a general guide.
 
Hi Troi,
It's really hard to define these numbers, especially with the advent of so many different lighting technologies (T6, T8, T5 and so forth). Ever since I got a meter I just look at PAR values, so I'd have to reverse engineer the wattage specs.

I like to use the analogy of a car when talking about lighting. If we consider that the plant is the motor, then the fuel is CO2 and the light is throttle. So, light simply allows the car to travel faster or slower, to use more fuel or less fuel as required.

In the OP's case 18 watts T8 over a 30USG tank gives a measly 0.6 wpg and I think that was his (her?) concern because at face value this number looks really low. However, if the tank is 15 inches deep, the PAR at the substrate will be somewhere around 15-25 micromoles at the substrate level which is low light. This means that the RATE at which the plants grow will be slower. As the plants grow and they get closer to the surface, the PAR is at a higher value and so they will accelerate their growth as they get taller.

This is either good or bad depending on one objective. Slower growth means that the OP might get impatient but it also means that the likelihood of algae is also very low. I think people tend to associate more light with greater health, but this is a myth. There is no relationship between the PAR and the health of the plants - unless the PAR is below the minimum light required for survival (LCP).

If you are using T8 or T12 you could easily quadruple this wattage (or the number of bulbs) and still be OK. That means faster growth and higher CO2 consumption. This will still work well, but only in the sense that the growth rates will be faster. It will be "unwell" in the sense that maintenance requirements will increase proportionately, CO2 consumption will be higher, nutrient requirements are higher and, problems that do occur will occur more quickly and are less forgiving.

Now, granted, I specifically tried to steer the OP away from becoming a Klingon because I know it's very tempting. But, because I know that you have a lot more experience, the answer that I would give to you would be 40-60W T8 on this size tank. This produces growth rates at a fairly decent clip, allowing the tank to fill in quickly, especially if you will use your high nutrition organic soils. If you switch to, or add T5 then just divide the number by 1.4.

Not a direct answer I know. Sorry...

Cheers,
 
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