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Setting the light level in my 24in deep tank

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What's the best method to figure out the lighting level/photo period for my new, deep, planted tank?


I've just set up this 30g high.  It's 24x24x12.  It's low tech (ferts but not CO2).  It has one of the new coop lights.  The substrate has some flourite black in pouches, but mostly it's aquarium gravel capped with black diamond sand.  Lots of root tabs.

It's planted with

  1. Corkscrew and jungle val
  2. Dwarf saggitaria
  3. java ferns
  4. pearl weed
  5. hornwort
  6. Anubias nana petite
  7. One Crypt
  8. A narwhal and a Disney queen.

The last tank I set up promptly became an algae farm, because the light was too high.  It's taken a long time to get back under control.  I would very much like to avoid that happening again.

So, my questions are:

  1. What's the best method to figure out the lighting level/photo period? 
  2. Should I start low and turn it up if no algae appears?  
  3. Start high and turn it down until algae stops growing?
  4. Any guess about what a good starting point for 'high' and 'low' would be for a tank this deep?


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Looks lovely! You can try 8-9 hr photoperiod to start. Just beware of plants obstructing the light by growing up to cover the surface.

Healthy, plentiful plants will use up the available nutrients and keep algae from getting a foothold. 

If it's a new tank, algae will show up. Amano Shrimp are helpful to trim any excess that appears.

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If your goal is to try to avoid algae completely I would start with moderate intensity (maybe 50%-60%). And a short photo period (6 hours). I would only increase intensity or duration if I noticed plants struggling. 

Personally I like to start with a lot of light, welcome algae growth, dial it down once a week until algae growth stops and then leave it there for a while. Eventually I will start increasing the intensity again If I think more efficient plant growth is possible. 

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On 5/15/2023 at 8:32 PM, memorywrangler said:

What's the best method to figure out the lighting level/photo period for my new, deep, planted tank?

I would monitor your plants that are in the front and carpeting.  That would be my go-to in terms of tank health.  If they have algae you may need to adjust light (up or down) or a variety of other things like dosing might be the cause.  Whatever that plant is doing is how I would view things.  the longer stems and taller plants you can trim down if need be.

Edit: keep an eye on the anubias too.  It's a lowlight plant and right under the hotstpot.  If you run into issues I would say raise up the light or move the anubias to the lower light spots.

Edited by nabokovfan87
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I'm at 21" deep, the biggest trouble I think with deep tanks in general is you almost need to blast the light to get it down deep. The method I used to figuring out light strength was to watch how plants react. Are they opening and closing with the light? Are they thriving or slowly dieing?

It's a tough balancing act, trying to split between too much light up top verses too little light at substrate level. Over time you'll also recognize where your high light areas are at substrate level. You might have to also rearrange your tank and plant according to bright spots or dimmer areas of the tank.

For me when 'figuring it out' I would also plant the same type of plant/stem in various areas to see where it grew best or raised plants up with planters (in my journal for refrence) for those that needed more light. Its a process, don't expect to find a definite answer on a message board, trial/error and patience is the key. Good luck!

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