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Hi everyone, first time poster here, so try and go easy please. I'll try and supply as much info as I can straight of the bat.

I'll start off with some background info about my fish/planted tank experience.......oh wait!!! I don't have any! Well that was quick.

I got given a 100l tank a couple of months ago, unfortunately the hood looked as though Michael Flatley had done a show on top of it, but the lights(dual 25W t8) were ok so I just threw together a make shift hood to house them in, done a fishless cycle, added plants and then fish. So far everyhings been going great.....until now!

I'm now worrying my lighting may be to strong for non co2, but I'm not 100% sure.

Upon original research I came across all the old WPG methods for light intensity and that's what I based things on but have now realised it's more about PAR levels. There's not much info out there that I can find on testing PAR for t8s, but the info I have found is leading me to believe the combination of my lights and my substrate to light distance is putting me a lot higher than I originally thought, causing me algae issues. This is what I need someone more experienced to confirm or deny.

This is the thread that has led me to my assumptions.
http://http://www.plantedtank.net/forums/10-lighting/184368-lighting-aquarium-par-instead-watts.html

Some info on setup:
Tank: 100l (36Lx15Hx12W)
Lights: Dual t8 25w with reflectors (13"-15" from substrate)
Filter: Aquamanta EFX200 + Hydor Koralia Nano 900 Pump
Ferts: EI method at 1/4 recomended dose + Excel 1.5x recomended dose

Any more info needed, just ask.

TIA

Ronnie
 

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I think you are right about having too much light to use without CO2. But, there is an easy way to drop the intensity significantly. A single layer of ordinary (in the USA) gray fiberglass window screen between the light and the water will drop the intensity by 40% Two layers will drop it by 64%. If you have around 70 PAR as I suspect you do, a single layer would drop that to about 40 PAR, which is low enough, but you should use Excel, or equivalent, to get good plant growth with little algae. The window screen materials you have access to may result in more or less PAR reduction, but I doubt it would be a drastic difference.
 

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Hi Ronnie,

Welcome to the forums!

For what it's worth, here are my reflections on your system.

15-20 years ago, before cfls, LEDS and PAR as a common measurement (these were the wpg days!) and abundant virtual forums, I ran a quite similar system to yours (36"L x 16"D x 12"W) with ~13 to 14 inches of water over the substrate, using a 25 watt t-8 (don't think there is a reflector) and a 30-watt t-12 (good reflector). My memory is that this considered to be a good light set up for plants at that time; no mention of using CO2. I had this system running 3 or 4 years; recently resurrected it, actually, and set up my first dirted tank using these old school lights.

I never had a significant problem with algae, and always used a 6 or 7 hour photoperiod. Just scraped a bit off the glass when I changed the water, and it was generally diatomaceous algae, not the fuzzy stuff. The tank got some indirect natural light most of the time; it was set up in quite a few different locations in my student days. I always had an abundance of fast growing stems (ludwigia repens, Brazilian pennywort, green hygro, unidentified others), and they grew very well once established. Letting them cover a bit of the surface area does reduce light transmission. Bulb plants like nymphae stellata and an unidentified aponogeton did well, as did java ferns and mosses.

I haven't ever used CO2 or Excel/equivalent on this system. Personally, I consider my tank to be a medium light planted tank at about 2 watts per gallon.

If you want to use Co2 or a liquid carbon supplement, of course, go for it! Based on my experience though, I doubt you have to (but your tank will let you know).

In addition to the window screening method to reduce light transmission (sounds like a great idea), here are a couple of other ideas.

1) You can use floating plants (frogbit, giant duckweed, red root floater, water wisteria, pennywort etc.) to help shade the tank. However, you will need to regularly remove some of the floaters once they are established so a bit of light gets through! An added benefit of emergent plants is they are good at using up nitrogen compounds in the water (which you the remove when you remove excess floating plants), and fish seem to appreciate them.

2) Light choice. You can reduce the "useable" light in your tank by having one of your bulbs be less "plant friendly." For example, freshwater plants apparently don't use the actinic light that reef keepers need, but actinic light really brings out great colors in many freshwater fish. Using a 50/50 Actinic/10,000 K bulb will cut the useable light to the plants, and make many common tetras, like neons and cardinals, and German blue rams, look awesome. I did use one of these on my system for several years because I liked the visual effect, and didn't have algae problems. I believe Coralife still makes this bulb in t-8.

3) Add a glass canopy (I used one). Cuts light transmission maybe 10%, greatly reduces evaporation, and keeps fish in the tank (and cats out!).

Good luck!
 

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Thanks for the replies folks!

This thread contains all of the information you need including output of T8 bulbs from reflective and non-reflective fixtures.

http://www.plantedtank.net/forums/10-lighting/184368-lighting-aquarium-par-instead-watts.html
This was the link I thread I tried to link to in my OP. Cheers

Hoppy!

Thanks for the confirmation of my thoughts and suggesting ways of lowering the PAR. What you thought I might have was around the same PAR as I was estimating but I was thinking of another way of lowering it. As I mentioned in my OP I had to make a new hood for the tank and made it so it can be suspended from the roof therefore allowing me to raise the height. Would this work? If so, what would you raise it by to get the desired PAR? I was thinking around 4".

Snakey

Hi, thanks for the welcome! It's good to know someone else has a similar set to mine, not many people out there still using t8s anymore I assume.

Non CO2 is what I'm after(to begin with anyway) but I'm dosing excel for that extra boost. I like the thought of some floating plants though, especially if I end up lifting the hood a touch, it will be something nice to look at rather than just rippling water.
 
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