Algae, Nutrients, and Light

It is no secret that algae grow in response to light. All other things being equal, the low light aquarium will have fewer algae problems than the high light aquarium. Isn't that the whole basis for keeping the light intensity down to what is needed for the goal you have for your aquarium?

 

I haven't seen any good discussion of length of photoperiod vs algae problems. I do know that some people always say reduce the photoperiod to 8 or 6 hours when you say you have algae of any kind. I wonder if there have been any tests done to demonstrate that long photoperiods increase the chances for having algae attacks. I can see how that might be a contributer to algae.

 

I would naturally assume that would happen, but I think that's due to the way she is growing plants, not the lighting itself. Since she is relying on her CO2 to come from the atmosphere and also biological action within the substrate, she is dealing with a pretty limited (but continually replaced at low rates of speed) supply of CO2 compared to injected tanks. If she keeps lighting levels low, that will allow the tank's naturally generated supply of CO2 to keep up with the plants needs.

If she just increased light levels (keeping the photoperiod the same) the plants would begin wanting more CO2 than the tank conditions would be able to supply and/or sustain, so plant growth would suffer and algae would get the upper hand.

If instead, she kept the light levels low and just increased the length of the photoperiod, the plants' rate of CO2 uptake would remain the same as before, but because of the longer photoperiod the plants would end up receiving more total light each day (energy) and thus be able to absorb more total CO2 (while still absorbing it at the same slow rate) over the course of a day than they could before. That would allow the plants to increase their growth.

I think of it being like a car that has a constant slow stream of gas going into the gas tank at all times. The stream of gas is equivalent to the incoming CO2 in a "natural" or "Walstad" aquarium. If you try to go 80mph in the car for 8hrs a day (higher light levels and shorter duration) the car would need more gas than the slow dripping into the gas tank could provide. That would mean that you would end up driving really short distances very fast and then running out of gas and being stuck for a while until the gas levels built up again within the gas tank before you could start out again. This would happen many times in the course of that 8hr period. You wouldn't end up getting very far that way, because it is very inefficient to keep stopping and starting the car, because the car has to warm up again each time and it will use more gas every time it has to accelerate from a stop.

If instead you only drive 20mph and do that for 8hrs a day (lower light levels and the same lighting duration) the incoming gas would keep up with the engine's needs for the entire day and you would cover more total distance in that same day (versus scenario 1) because the car wouldn't be losing as much gas to the constant stopping and starting inefficiencies and other losses.

Now if you kept your speed at 20mph and then decided to drive 12hrs a day instead of 8 (same low light levels but longer duration) you would still never overdrive your fuel source, but you will be driving for a longer amount of time each day, so you would be able to drive more total miles in a day. More total miles = more plant growth.

I could see having a longer photoperiod helping plants that usually like higher light to grow better in lower light tanks as well, because the longer photoperiod would help the plants to make sure they could keep themselves above the "minimum light threshold" they need in order to keep up with normal leaf maintenance and required plant processes.

To me the "minimum light threshold" is not necessarily a certain lighting level per se, but a certain amount of total light the plant needs to receive in a day in order to meet it's minimum energy needs for that day.

I have never tried longer photoperiods myself (over 12hrs), but intuitively I would think that periods over 12 hrs. or so wouldn't be of much benefit (and would only contribute to algae). I base this current belief solely on the fact that many of my plants begin closing up their leaves for the night even before 12 hrs of light is up. I could just be making an assumption that is incorrect though.

In a CO2 injected tank that was made sure to always have adequate CO2 I would think all that would matter (in as far as plant growth) would be the total light received by the plants each day, not necessarily the light levels or duration (as long as they were kept within the range of being usable amounts of light and usable light durations from the plants' perspective).

Since CO2 is tricky for many to keep stable and ensure is in adequate supply, having lower constant light levels and then using longer duration (up to about 12hrs max in my opinion) to increase growth levels would make for a more stable system overall than would be achieved from increasing the light levels in order to try and increase growth. More stable = less possible algae problems.

With all of this coming into play it truly points once again to it seeming like all that really matters is not the lighting intensity or the duration, but just making sure that plants always have all the nutrients and CO2 they need to keep growing at all times. That's what will keep algae at bay. As long as that is achieved, the specific lighting duration or intensity isn't really that important as long as the minimum levels are met.

Those are my current thoughts, beliefs, and experiences anyways, and all is up for change if new and trustworthy information enters the picture.

Have a good one, Jeremy

 

Speaking of Innes,

I have his book "Exotic Aquarium Fishes" from 1950. I still learn new stuff from reading that book, in many cases related to subjects that I don't hear talked about much today.

I also like occasionally reading the section about setting up your own aquarium where he explains how to build a nice slate bottomed aquarium with a DIY brazed brass angle iron frame and even how to make your own Bitumen (from scratch) for securing the glass panels.

Also, if I hadn't previously read his section on "aquatic enemies" I never would have realized what the thing was that landed on my hand while I was cleaning my 10 gallon tank that was loaded with lots of plant starts taken from a local storm water pond. It was a large dragonfly larvae. It was very unnerving to feel something touching my hand (in a tank with no fish) and then to look through the glass of the tank to see what it was and see that thing sitting there on the back of my hand. I had no idea a hand could be removed from an aquarium as fast as mine was that day. Things like avoiding accidental water splashing and drips on the floor while doing maintenance seem important most of the time, but occasionally they dramatically lose their importance in the whole scheme of things. That was one of those days. I actually got tank water on the ceiling, haha. I like adult dragonflies, but the larvae are mean looking.

Have a good one, Jeremy

 

What school did you get to do all that in? Sign me up

Here in the desert all we can do is test the different depths of sand.. results - a foot below sand is more sand.. etc...

-Nerb