Hi,
Thanks for providing the additional details. That really helps!
It seems that all of the changes you've implemented are the correct ones. Being Dennerle, the quality of equipment ought to be beyond reproach. I like the geometry of your spraybars (I use a similar setup) and I like the fact that you've sealed the sump. The gas turn on schedule relative to lights schedule seems reasonable to me. I'm much less in love with that textured background though, and I feel it contributes to issues with flow. But this can be compensated for by having higher flow throughput. You realize that for a high tech tank the 10X rule should be enforced? This means that you ought to have in the neighbourhood of 7500 Litre per hour of rated turnover. I don't recall seeing your turnover number for this setup. I'm also still a little unclear as to the placement of the diffusers. Are they mounted upstream of the spraybars, or did you say they were stuffed inside the spraybar? I assume that means at the upstream entry point of the bars?
It's probably debatable but I think that CO2 diffusion should occur well upstream of the spraybars to enable better dissolving of the gas in water prior to being introduced into the tank. This is just theoretical mind you but I prefer to NOT see any CO2 bubbles although there is the Barr concept of CO2 misting which sends fine gas bubble into direct contact with the plant surface. But I don't think this can be done very efficiently with our typical reactors, only with speciality equipment such as Mazzei injectors, which is an advanced high efficiency CO2 distribution technique. In your configuration the CO2 lost to the surface is very high because most bubbles head straight up and only a small percentage of the bubbles actually stay submerged for any length of time. These are the ones you see. if better mixing is achieved then there are fewer bubbles and perhaps some improvement in efficiency, which is pretty anaemic even in the best of times quite frankly.
I wish I had something more concrete because I'm sure I'd be flamed mercilessly at the merest hint of injection rate increase, and I don't think you'd be looking forward to pulling that background out, but I do have a few testimonials that flow rate and distribution were markedly improved when similar backgrounds were removed .
So the only thing left is flow rate increase, perhaps by adding Koralias? You probably don't feel too good about having to buy a higher rated pump I'd imagine. In any case I think the light intensity reduction will definitely help, though it might be a few weeks of elbow grease cleaning out the algae.
It's an expensive option, but if you're not afraid of Excel/Easycarbo/AE Equivalent you might think about supplementing this at least for a few weeks. This is the problem with a big tank, everything you want to do cost more than you bargained for. If you do go that route remember to include the volume of the sump in any calculation, so if the tank is 750L and the sump is 100L then you really have a 850L tank OK?
As far as that slimy algae you were talking about have you confirmed it is BGA? If your filter is clean as you say then one has to look at inadequate NO3 levels so try adding another 10 teaspoons KNO3 to your 1L mixture (or dose 100ml daily of your existing mixture) - if we are in fact talking about BGA.
Hope this helps mate.
Cheers,
