Greetings all. I'm setting up a 125 gallon (72 x 18 x 22) heavily planted aquarium. I'm running a 72" BeamWorks LED and two 36" Fluval Plant 3.0. I rented a MQ-510 Apogee par meter from Bulk Reef Supply and it's reading 170 par at the substrate with lights at 100%. I will be injecting co2 but those numbers seem too high. Am I using the meter wrong? Is that par too high for plants? Should I just dim them? What is the optimal substrate par value? Thanks in advance!

- Brett

Hi Brett, @bbuswell,

Welcome to TPT!

No, [email protected] seems about right for 2X Fluval 3.0 and a BeamWorks. That is a lot of light and will require a lot of CO2 and nutrients.

I certain would not run the tank with [email protected] without CO2 in place and properly adjusted or an algae farm and frustration will likely result. Without CO2 [email protected] is about as high as I would go. If you are not familiar with planted tanks start with low PAR and learn the basics for CO2 and nutrients first (for several months) then you can ramp up as you become more proficient. -Roy

Out of curiosity, did you measure PAR with the tank full of water and through whatever lids/canopies you might be using or was it an empty tank measured in air?

Thank you Roy. This is my first serious attempt at a planted tank but I've maintained community, cichlid, and reef for many years and ready for the next challenge. Definitely injecting co2 but now thinking I may need a reactor and not a diffuser as I’ve been reading 125 gallons is hard to get the proper ppm as it is. I’m thinking I will just dim the lights some, especially for the first few months. What would recommend for the par? I have a 5 lb. co2 tank and an amazon 2 stage regulator, ceramic diffuser. Going for a Dutch style as fish aren’t that important to me right now. Lot to learn in this space. I updated my profile, should have done that before I posted .

Bump: Yep, tank full and everything in place. Using BDBS and the water still has a slight tint... those Fluval's are intense!

Hi @ bbuswell,

If this is your first planted tank start slow. [email protected] measured at the substrate. The diffuser may give you sufficient CO2 for the lower level of light intensity however as you increase light intensity the amount of CO2 and nutrients required will increase so you may need to look at alternative CO2 delivery systems later. I have a 5# CO2 tank on my 75 gallon and it lasts about 2 months....I am not running maximum CO2.

Appreciate it, that's what I'll do. Will I have any plant selection restrictions at 50? Wanting to grow a carpet at one end with denser planting at the other.

make sure you measure the PAR at the corners of the tank too, I think 50+ is usually enough dwarf baby tears and monte carlo. nd yea start low and ramp up or you can plant really heavy at the beginning.

I ran my contest entry at about 163 PAR, it's doable but expect some hiccups along the way: https://www.plantedtank.net/forums/1...l#post11266537

If you decide to go that high I would consider upgrading to a 20-lb co2 cylinder and getting a Dwyer flow meter instead of a bubble counter.
as for reactors, the Sera 1000 is pretty good from what I heard if you don't feel like DIY'ing your own Rex or Cerges.
Green Leaf Aquariums also releasing their own in a couple of days


@burr740 run's his main tank at 100+ PAR and is a dutch scape: https://www.plantedtank.net/forums/1...er-volume.html
@Greggz has a nice tank too running high PAR(100+, maybe 130?): https://www.plantedtank.net/forums/1...l#post11272413

That reactor looks awesome! I’ve been itching to try one, but I don’t like the idea of flow loss.

Also, I’ve found that running 100ish PAR is very doable so long as you’re on top of maintenance and you have enough plants to soak it all in. My Seneye measures my tank at roughly 114 PAR at the substrate in my nature scape 40 breeder.


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Thanks for sharing that. Those threads should keep me busy for awhile. The lowest measurement I could find in the corners was 105. Your tank is beautiful and what I'm going for. Wish me luck, I'm sure I'll have much to ask and post in the coming months. Cheers!

Hi Brett, @bbuswell,

Why not hold off on a foreground/carpet until you get comfortable with your tank and fertilizing; typically for a good carpet of Marsilea minuta I have +/- [email protected]

30 gallon, CO2, Marsilea minuta in foreground right

It is not about PAR only. You can have 68 PAR or 170 PAR and both can work. The missing variable is time. Time with PAR gives light energy per day. You can have

10 hours of 68 PAR a day, to have 680 PAR/hours a day, or
4 hours of 170 PAR a day, to have 680 PAR/hours a day

The plants are more less going to be driven by the same light energy and therefore need the same CO2 and fertilizer quantity. Considering your aquarium height, you may prefer stronger light. These are the same principles as with reef aquariums.

With 125 gallon you will find a CO2 flow meter and a CO2 reactor more useful.

Thanks for sharing. Those threads should keep me busy for awhile . Your tank is beautiful and the look I'm trying to achieve. Wish me luck, I'm sure I will have much to share and ask over the coming months. Cheers!

Do you think it would be better to fully plant everything at once, maybe dry start, or slowly add plants? Would a slow add complicate balancing? Don't want to move hastily, still learning

EI ferts routine appears fairly straight forward.

Bump: I appreciate that explanation, thank you!

Hi Brett, @bbuswell,

I plant my tanks all at once. Some plants will thrive, some may not. If some species don't do well I try another species until I find ones that work in my tanks. Some plants I just don't do well with, that's OK. I just find a different variety that does like the conditions in the tank. Since I enjoy my fish as much as my planted tanks I adjust the water conditions for the fish and then find species that will do well in those conditions.

As Roy stated, this method has been working for me for the last few years in my big rainbow tank. Fortunately there are a LOT of different plant varieties out there to choose from.