Try not to get too downbeat. I had exactly the same issues on my first come-back (after 20 years hiatus) high tech tank. Very similar to your layout (though on a smaller scale) [
Journal] in terms of large arching hardscape, and I encountered similar challenges with flow and distribution. In the end I really struggled with stems because the lower parts were so easily overshadowed, and I couldn't get sufficient CO2 down to them, and I also got regular BBA and staghorn on the plants on top of the wood nearest the light. Stability in the long run, and a high density clean-up crew, were the main solution, but I still had to occasionally apply Excel to kill off any excessive algae growth.
You might be able to improve your flow pattern by moving one of the inlet/outlet pairs - are they both in the rear corners? Maybe the pair on the left would be better right to the front of the glass, and the right hand pair, right to the rear corner. That would help you get CO2 down to the front substrate where you're currently having issues.
Thank you for the encouragement, it's good to know I'm not alone struggling like this. I read so many journals and watched so many videos on scaping that I thought I'd done everything "right" when setting the tank up, not realising that my giant hardscape would totally screw it!! My desire for a dramatic look was too strong. I have exactly those problems you said with stems - they grow in one area quite well and the rest are tragic looking. I don't need loads of stems in this tank (though it would've been nice), but only a few things are happy and there's so many gaps in between. I just wanted that sweet sweet lushness!! As always fishkeeping is all about learning.
Which cleanup crew did you find useful? I have been thinking of trying to get more amanos again, I have cherries and otos in there but they don't really do much as I'm not sure they eat the algaes I have. Also have read that blue gobies are tough algae monsters but idk, will think about that one.
Sadly I don't think I can improve the flow any more with the filters, because of the wood placement. I have improved it a lot from what it was, but this front deadspot is so annoying.
At first I had the filters both going in the same direction like, and basically the whole back was a deadspot.
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But now they're like and a lot more of the tank gets good flow.
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I could fix the front deadspot if I could reverse it like this (the deadspot would just go on the sand)
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But the wood is in the way of doing it this way, it would baffle the flow immediately out of the pipe.
This is what the flow is doing atm. I'm wondering if a power head would be a possibility in the front left near the bottom? IDK sounds ugly but maybe is required. Alternatively thinking (but hoping to avoid) of swapping over the "carpet" area with the sand area, but I really don't want to do this because it'll be loads and loads of hassle and very messy. Plus the fish seem to like the scape as it is, the sand is right by the dark archway so they feel safe, and that's where the baby kuhlis live amongst the rocks at the edge of the sand and I'd be worried about hurting them moving it. That is one of the reasons why I've put up with the dodgy plant growth, the fish are happy at least lol.
Like wooki says don't get down about it, this high tech malarkey is hard work, especially in comparison to low tech set ups, I'm sure you'll turn the tank around.
Not sure if this would be of any use to you but I'll have a variety of trimmings over the weekend, nothing exotic, mainly fast growing stems (sessiliflora, polysperma, hygrophila difformis) and some vallisneria plantlets. You're more than welcome to have them if you temporarily want to increase plant mass, without any cost.
Thank you for your kind offer, I would love the trimmings! One of my suspicions is that just adding more plant mass would help a lot to change the tide for good, and at the very least cover up that bloody soil. I'll PM you.
Low tech is just sooo much easier. Even when they're unbalanced with algae I found it so much easier to get it right, and even with algae the plants never dropped dead on me the way they have here. I refuse to give up, but I am super pissed off about it right now!!