Flyfisherman said:
..6 - 8 weeks ago I started the running in period of my 2080 with a mixture of media - old media from my Ex1200 and new media from the 2080 - bacteria colonization. Last Saturday 02.05.2009 I decided to remove the all the Ex1200 media and replace it with the rest of the 2080 that had not been used - now the filter is running with eheim media, fill the canister back up with water from the tank which meant the water level in the tank dropped by 25 litres (canister capacity) which means a reduction in overall depth of water by appox. 1.5". I did not top up the water level as I was due to do my 50% that night, so i left it. Prior to changing my water Saturday night,I noticed that my HC was covered in tiny bubbles and my other plants were pearling. Last night @ 18:00 - water level at the correct height no bubbles on HC, More HC added of which I had bought in the afternoon, popped them into the tank, still in their pots and 1 hour later tiny bubbles appeared - 3 hours later they were covered in a mass of tiny bubbles, my water is not gin clear - it has a very slight haze. Co2 levels are o.k - Cal aqua reference solution / indicator solution are identical in colouration in my Cal aqua double drop checker. So the greater the depth of water the more light is required to penetrate through the water - proved this on Saturday with a reduction in water depth / Sunday increase in plant height...
Well, I'd have to say that this really doesn't prove anything because fundamentally you have not isolated "distance-from-bulb" as the only changed variable. You are drawing a conclusion from circumstantial evidence.
When you drop the water level you affect flow as well as the amount of time it takes to saturate the water column with CO2. The ejection of oxygen depends on the
rate of photosynthesis, which in turn depends on not only light intensity, but nutrient uptake rate as well as CO2 uptake rate. There is only one way to quantify the light intensity level change and that is to measure directly with a PAR meter.
The effect should also be repeatable and it should be magnified by degree of water level change if this is the only factor. So a 3 inch water level drop should perhaps produce either more pearling or pearling sooner (although the hydrodynamic effects wouldn't be known either).
What you could do is to keep the same water level and raise the pots by 1.5 inches or, if possible, drop the light source by that distance.
It's still not clear to me what filters are operating in the tank or were operating in the tank. Is it powered by both a 1200 or a 2080, or both - and has that changed over the last few weeks? There is also mention of media change but it's not clear whether the filter has had a media volume change or just a media swap. Replacing or removing or adding media to a filter changes the flow rate so this will have an effect as well.
Certainly, murky/cloudy water will change the equation but then consider what will happen when the water clears. Would the effect not be canceled once the water clears?
So I can't say for certain whether your conclusion is incorrect, only that the rationale leading to the conclusion is faulty since you have not taken into account all the possible variables associated with a drop in water level. Basing a future lighting upgrade solely on this rationale could cause trouble later on if it in fact turns out that the pearling was not lighting related, and in fact you could be buying yourself more trouble if the factors leading to the pearling are not fully grasped. That's why I advise to maximize CO2/nutrients/flow first. A green dropchecker doesn't necessarily mean that you have optimized your CO2. Try driving the checker into the yellow for example, being careful not to gas your fish! After you've pushed the limits without success then you can say "OK I need more light".
Paul, don't get me wrong. I'm the worst of all the lighting fringe lunatics/extremists. I despise looking at dim tanks. I'm just trying to point out that The Matrix has programmed everyone to think that adding more light solves their problems when in fact just the opposite is true. Sometimes, yes, there's just not enough light to grow some plants in some tanks, but more often than not the limiting factor in a tank is inadequate CO2, flow or nutrition and adding more light simply exacerbates these problems. Now, if you want a brighter tank then by all means go get more light - but you had better have a firm grip on these other factors to be able handle the higher demands of higher lighting.
Cheers,