DHenry said:
...So in theory one could have a low light tank with low co2 and low nutrients but a reckon it would be a hard balance to find...
No mate, this is much easier to accomplish than trying to max everything out, although it's certainly more difficult than a non-enriched tank. As I mentioned before, the reason people have so much difficulty with high tech tanks is because they automatically assume that they need high light. How many times have you seen people post, where they buy a tank set with hood and lights, and the very first question they ask is how to add more light, or how to upgrade from T8 to T5 because they assume that the lights that came with the tank are not strong enough? I see a question like this almost every day. If the poster merely improved his/her flow rate and concentrated more on the rest of the equation they wouldn't have nearly as much difficulty. One can use low tech lighting and high tech everything else and the chances of success are much higher. When you tell them this their response is inevitably "Oh but I want to grow demanding, high light plants". The real answer is that there are no such things as high light demanding plants. Someone simply coined the phrase and suddenly it became "fact". You can find this bogus phrase listed in almost every plant catalog and uttered by almost every plant supplier, even by people who should know better.
niru said:
1. Given a high light, CO2 tank, if one 1st lowers the light (period & intensity) keeping the CO2 and ferts same as before, then did I get it correct that the plants are kind of compelled to utilize these to the fullest available for that reduced light (as you mentioned above) ? And why exactly is this? (Something like putting tempting food in front even if theres not much appetite gets vulnerable souls to over eat ??) Of course going the other way is real no-no (low CO2, ferts but high light), but why is low light and more than needed fert/CO2 also equally (??) bad?
Hi niru,
Well, all organisms are programed for success. Whatever is available to them they will take. If you keep feeding your dog he/she will keep eating and will keep growing. This is the only way an acorn becomes an Oak. Since a plant will continue to grow until it dies for whatever reason (predation, disease, trauma) it will always attempt to maximize it's uptake of nutrients and CO2. If more CO2 becomes available, the plant will utilize it. The only thing that will slow the CO2 uptake, at any light level, will be the physical and chemical limitation of the uptake mechanism itself. At some point, adding more CO2 does not result in any additional growth rate increase simply because the physical limits of the movement of CO2 across cell boundaries and the physical limits of the speed of it's transport and use. From the plants perspective, at a given light energy level, the point at which adding more CO2 does not result in improvement is referred to as "unlimited CO2". It doesn't actually mean that there is an infinite supply of CO2 (because of course that's impossible) but from the plants perspective, it can't use any more so this is the same as having an unlimited supply. This is exactly the same with nutrients. For a given lighting level and CO2 level you can continue to increase the nutrient loading until a point is reached where adding more nutrients does not result in an increase in growth rate. The tank is then "nutrient unlimited". This is the principle of EI by the way.
Light energizes the plant uptake mechanism, therefore, increasing the light will enable a high value for the "unlimited" CO2 and a higher value for the "unlimited" nutrients. At some point adding more light does not result in increased ability to uptake more CO2 and nutrients, so this is light unlimited.
niru said:
2. If one wants to "convert" a working high light+CO2+fert tank into a low tech tank so as to minimise organic waste buildup, whats the best strategy and over what timescale, so as to ensure minimal algae issues and plant deterioration
The answer is easy. Look at the equation. All you have to do is to lower the light intensity, wait a few weeks, then lower the CO2, then wait a few weeks, then lower the nutrient loading, then wait a few weeks, then repeat the cycle.
Obviously, the higher your starting point the more difficult and the longer the time required to pull this off without any difficulty. Another, more extreme strategy is to perform a blackout, or to just shut all the lights off and to shut the CO2 off. After 3 or 4 days without light and CO2 we can then resume the new low lighting level with reduced nutrient dosing and non-CO2. The response of the tank depends on a lot of factors such as temperature and species. Lowering the temperature by a few degrees helps lower the demand for CO2 & nutrients. The main factor, naturally is what the final lighting levels is.
Cheers,