You're definitely right on track! Great job and you've really got all my ideas covered. Gutter guard worked well for me. It allows a lot of flow too, compared to a weir with teeth in my experience.
You can add a small vortex to the pump outlet in the sump and plumb the Co2 directly to that. solve any lossI hope the sump don't leak too much CO2. I will reduce the surface agitation by making a full syphon with bean animal system. Do you have a sump? Can I start a low tech tank with this kind of filtration?
I still evaluating my fish option:
1.- Angel fish, tetras neon, axelrod rasboras, cory cats
2.- Royal blue discus, axelrod rasboras, pearl gouramis
3. Schools of danios, tetras, rasboras…
I can do 2 inches of soil and 2 inches of sand, how deep my substrate can be? Can you do hills with this kind of substrate?
I would really do more water changes than 25% once every 3 months.
Your fish would thank you for it.
What is the line of green stuff in the top back?
i would listen to the tank to see if you need a water change or not. many people here have a made up rule in their head that you need to change #% of water every 7 days. those are all made up rules. I think for a tank like yours, you're doing fine. every 3 months - 4 times a year is fine. as long as you have plants, there is a eco system going on and it's balanced. only the newbies who mess with their water and throw off all their settings and almost comes crashing is when they need to hit a "reset" button and do a water change. but if you have everything balanced, its fine.In the last 25% water change the hole ecosystem stunt, so I'm still deciding what is the best course of action. Some say that no water changes for a low tech tank are fine and some say that 2 or 3 each year. The last water change was on August and right now everything seems to be normal. The evaporation in this tank is amazing so daily we have to fill between 2 to 4 liters of water. So if you do the math every 3 months we refill more or less 25% of the water, additional to the 25% I was doing every 3 months. I know that this doesn't help get rid of the toxins but the ammonia and nitrite are 0 ppm and the nitrates are between 10 and 20 ppms.
The line of the green stuff is the return overflow that is cover of brown diatoms. Part of the overflow is fill with substrate because we want to grow some emerged plants on there.