SkrimplyVixen

I used to have somewhere around twenty aquariums of various sizes. Due to the time involved with maintenance and cost of equipment needed to support that number of tanks I have always gone with low light, low tech setups. I moved to a different state with a newborn in tow and decided it was the right time to downsize my hobby, I now only have one tank. Since it's only the one, I figure I better "make it good" and strive to get what I've always wanted in a planted tank.

My delimma here is not knowing what the threshold is for light limits in relation to requiring CO2 injection. My issue with going high tech is that I live in an area that experiences power outages 2-3 times each winter due to high winds and ice causing downed trees. I could run equipment with our generator, but would have much more peace of mind with a setup that can thrive with dosed ferts and a liquid carbon source such as thriveC or the flourish/excel combo that I've used in the past.

My aquarium is 65 gallons, it measures 25" tall from edge to edge but will be about 23" from water line to substrate once I have my soil and sand cap in there. Ideally I would like to grow a dwarf hairgrass carpet using the dry start method, but am absolutely not dead set on DHG...monte carlo, microsword, etc look just as nice to me. The light fixture that I have now is a beamswork DA 6500k 0.50w LED, it has 5 rows of white and blue lights. It has done very well for me in the past for growing anubias, java fern, hornwort, etc but I don't think it is strong enough to support the look of a carpeted plant scape that I would like to achieve. I am considering the options of either buying a second fixture exactly the same as what I have, or adding the Beamswork FSPEC 0.50w 6500k fixture. Bumping that up to a 1w and/or 10000k fixture is also a possibility if needed. I am just not sure what to choose in order to have strong enough lighting for carpeted growth while not pushing the setup over the edge into injected CO2 territory if it's at all avoidable.

Thanks in advance for taking time to read and/or respond!

hoppycalif

Welcome to APC! And, that is the right question to start with, in my opinion. Unfortunately, there is no widely agreed upon answer. For example, in my opinion, once you exceed 60 PAR or roughly that much, you need to use pressurized CO2 to have any realistic chance of succeeding in avoiding algae problems. I know many people disagree with that, and believe the number is much higher.

Start by accepting that you can't substitute any method of characterizing light intensity on a planted tank other than PAR. So, whatever intensity you believe is the limit for no CO2, you have to have a way to pick the light fixture that gives you that amount of PAR. I tried to do that several years ago when I wrote: https://www.plantedtank.net/forums/1...ead-watts.html Since then there have been many LED light fixtures on the market, and few of them supply the PAR data needed to evaluate them. It has also been some time since I last did a thorough job of looking for PAR data for all of the LED light fixtures now available, so I hope someone else is willing to tackle this.

One more point: plants do best, and look their best, if the light has a good amount of red light in its spectrum. Just using "white and blue" LEDs is not a good option.

SkrimplyVixen

Thank you for your advice. I appreciate the link you provided as well! I've been a lurker on this, planted tank, and the Barr Report forums for quite some time and that post you shared rang a bell with me, it may very well have been my first intro to PAR values as a concept some years ago and I will definitely read over it again now that I am trying to expand my knowledge. I think it was on planted tank forum that I saw a comparative graph posted showing the PAR values of two different Beamswork fixtures at varying depths with and without water. Given the info there along with what you have noted about white/blue light vs red/green I am thinking that the FSPEC fixture will be the way to go for me. I just am not sure what the differences are between the DA/EA designations, 1w/0.50w and 6500k/10000k. I'm sure the info is out there, I just haven't dug around for it yet.

I have also found a chart on seneye that gives a breakdown of what PAR values are preferred by some commonly kept plant species. I was happy to find that as a point of reference!

I wonder if the variability existing in regard to what PAR values constitute the need for CO2 injection lies within the options chosen for filtration and substrate for any given setup. For example, an aquarium with soil substrate and gentle/minimal surface agitation would require less CO2 be added to the system than one with inert substrate and a lot of surface agitation even if both have the same PAR value at the substrate level.