[Clintaceous]

This question popped into my head the other day, and thought I'd ask you guys your thoughts. If this question might be better in the general section feel free to move it, but my main concern is in regards to PAR.

So I've had a high tech tank now for a few months, and I'm trying to get a layout that I like. To help try and grow my plants as fast as possible to fill in my tank (as well as help my more needy plants, like Ludwigia glandulosa), I upped my light and CO2 (1pH drop, so should be 30ppm) and started monitoring my ferts. However, I'm 100% certain I overdid it with the photoperiod, and perhaps light intensity too, leading to a hair & staghorn algae outbreak. After cleaning the tank and filter, checking nutrients and attempting to kill it off with H2O2, it still is here. This leads me to believe my lighting is on too long, too intense, or my plant mass is not enough yet. For the record my lights should be somewhere between 100 & 120 PAR, with a photoperiod of 12 hrs (don't laugh, I learned my lesson! It would be more like 9 hrs of full light with a 1.5 hr sunrise/set, but I understand now its lots if light, and I'm slowly reducing the photoperiod first.) Doing some research, I've learned that as your lighting increases, so too does there nutrient and CO2 demand. Easy enough concept to grasp, but then I realized for most of us, CO2 can only go so high due to fish, shrimp, snails and whatnot in the aquarium.

So if our plants can only have 30 or so ppm of CO2, at what PAR level is CO2 a limiting factor again? For example, would it be 100 PAR, and beyond that the plants need more CO2 to not be under stress? I'm curious because I know some tanks run 200-300 PAR with no issues, but I feel they have no tank inhabitants and thus the CO2 can be cranked to 11.

Edit: For the ease of argument too, lets assume a tank that is heavily planted with stems, and has moderate amounts of nutrients (10 ppm Nitrates, 1-2 ppm Phosphates, 10 ppm Potassium, 0.5 ppm Iron)

 

[moke]

slowly increase the pH drop to 1.25-1.30. increase surface agitation. look for signs of distress in your fish. i use 1.25 and my endlers still breed like rabbits.

 

[minorhero]

There's two other things you need to take into account. 1) There is more to fertilizer then what we can easily measure. So you may need to adjust things based on plant observation. If you check out some of the journals here of people running 300 par at substrate level (and there aren't that many that are active but there is at least 1 or 2), you will see they usually roll their own fertilizer. This is not something to take on lightly as its almost always the cause of problems when someone tries it who doesn't have a ton of experience and willingness to trial and error their way to victory.

2) Plant growth is the other thing you need to consider. I don't care how much light and co2 you pump onto anubias and java fern or similar plants. They won't grow very fast. BUT you need quick growth to soak up the nutrients you will be pumping in or you will get an algae bloom. The answer is stem plants. LOTS of stem plants. All the 300 par at substrate tanks are dominated (almost exclusively) by stem plants. They usually do not have higher co2 then a 1 ph drop because fish can't take it.

 

[CoveBeach]

Another thing is the term “densely planted”. This is a widely subjective term in that you might have a large number of newly planted plants that are not established, yet are adding a ton of ferts to get really fast growth which is what most seem to want and end up with super fast growing algae. I know i was guilty of it also but managed to get the tank balanced before it got ugly. There is a saltwater saying “ Nothing good happens fast”. Here is my process. I added plants in one shot with about 6-8” spacing trying to pay attention to form and location and light requirements. At that point my lights at even 90% were blinding. I dialed them back to 40%, added root tabs and was adding liquid ferts per bottle directions. This still resulted in algae and some plant growth. The addition of a fairly moderate stocking of fish made the algae slightly worse. At that point i got my CO2 up and running and for a few weeks the algae took off a bit, but with manual removal and the the help of 4 Siamese algae eaters the stuff left and has not been back.
Depending on plant variety the spaces filled in causing shade which i countered by bumping my light output slowly over time. I run a very long ramp up and down on my lighting which on paper looks like a ridiculous amount of time. Example: first sign of light is 8:25am ramping to full by 10:45 which continues til about 10:30 pm and then ramps down til about 2am (not sure as i fall asleep in recliner). The CO2 is on about an hour before first tank light and off about 10pm. This has resulted in weekly pruning to keep the jungle in check,kinda. Here is the blasphemy, i only pay attention to a few parameters. First off is Temperature, second is PH and third are the fish happy and stuff green with new leaves. Bottom line, it took 2 Years to get where i am now, which is grow—in and sometimes over grown and ridiculously over stocked with fish and inverts. If anyone is interested you can find more info at 245 Starfire “FishTV”
Or just message me direct, i check in most days.

 

[Clintaceous]

This is all really useful information. Thanks everyone!

So from what I've read so far:

• You can only do so much to get good plant growth. The key is to keep consistentcy, and if changes are needed do them slowly
• Pick faster growing species, such as stems (which is what 90% of my tank is) as they will grow faster and outcompete algae better than slower growing species.
• Excessively high PAR is a dangerous game if you don't what you are doing. Based on minorhero's comment, light drives up the nutrient intake need and if you aren't dosing the right nutrients correctly, your plants will suffer and get algae.
• Plants grown even at 300 PAR at the substrate can grow with 30ppm CO2

Based on this info, I feel much better about my PAR and CO2. To be clear my algae issue isn't that bad (only old growth on some TC plants is affected, and most algae is growing on the hardscape or glass which isn't much either). Knowing this, I'll just focus on growing the plants healthy. If the plants don't have algae, and new growth is healthy, I should have minimal algae in a few months