Hiya mate, yes knock the lights and co2 off an hour earlier than usual. If you've had advice to knock the lights and co2 off then maybe you should go with that. Then both of us don't have to worry about your tank while you're away
There's probably a crash course in quantum physics and an A level biology reason why this woukd be a good idea but I'm looking at it like this, Dosing EI is not something we have to do or the plants will fail. Its something we do because its a sure fire way of making sure there is an abundance of nutrients. Tested up to unlimited lighting.
My worry, and I think yours is will the plants run out of nutrients while your away and my best guess is the answer is no they won't. Based on this..
You are going to put more nutrients into your tank that your plants could possibly consume. Even if they had an uptake rate of 100% (Highly Unlikely) there would be some left over.
You're not changing any water so there will also be some more added by fish waste /filter etc. (Some people get away with this on its own)
You're using a nutrient rich substrate which will have absorbed and stored some.
Your plants have been living with an abundance and will have stored some also.
Knocking an hour off the lights edges your bets by slowing down the plants and brings the chances of running out back in your favour.
Could you add twice ei? You could, some people in here do and it would also stop you running out. It could be argued that doing this might speed up growth. Don't know if this would be the case if you knocked the lights off earlier.
What happens if the plants do run out? Nothing much I wouldn't have thought in that timescale. Some people here deliberateley starve their plants of nitrate to get redder colours for photos without destroying the whole tank.
EI dosing is everything in excess not the minimum you need. A lot of the problems people experience through lack of nutrients is because they have done it constantly for a while. You will have done this for one week out of 52. In fact week one your tank is going to be no different. Week 2 how much different will it be? Not much I'm guessing. You'd have missed a couple of doses and a water change that's all. If you do 2x50% changes the week before you go on average you haven't even missed a water change.
The traces may run out because these don't last in the water for too long but they are traces so as long as there's some it'll be ok.
I don't think you'll run out of macros and if you do it would probably be in the last couple of days (if at all). Worth remembering that if on the last day there's 1ppm of nitrate left in the tank the plants won't ignore it just because its not at EI level. It'll just use it for food like any other time.
Anyway, that's just my opinion. It could be all wrong
but I suspect you are going to miss your tank a lot more than its going to miss you
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