What shape is your prospective tank? Tall/shallow? Rectangle/square?Cheap lighting = chihiros a series or rgb / desk lamp with a 6500k bulb
Eheim filter is an investment you won't regret. Connect some transparant tubes with lily pipes and voila ada style. I would aim for a filter that pumps 10x your tank per hour. Example if your tank is 20 gallon get a filter that claims to pump 200 gallon per hour. This way you have plenty of flow which is nice for a high tech tank. Add some seachem purigen on top of it
Filter media setup
ADA 60p is a great size to begin with not to small not to big.
Rimless tank great choice
Buy hardscape and play in a cardboard box(same size as your aquarium) to get a scape that you like. When you like the scape, set it up in your aquarium. Follow the rule of the thirds (golden ratio/focal points), watch for inspiration tanks and try to "copy" them. Make pictures of your tank and ask for feedback. (on pictures you can improve things better than from watching it in real life IMO)
Get a good rich substrate with ferts like ada aqua soil, tropica etc. Make sure to cycle your tank which is easy with new ada aqua soil as it leeches ammonia for 2-6 weeks.
A co2 system is a great way to grow plants better / more lush a.k.a. that something nice and beautiful you are aiming for. Also easier to fight algae.
Important factors for plant growth are fertilisers, lighting and co2.
I still miss a ton of things probably you need to read a lot over and over again about this subject.
Do as much research as you can. You will benefit from that! Be patience in this hobby
Square will let you hide your tubing without significant obstruction to water flow (at least no more obstructive than side mounting outflow in a square tank)
Try to do your heat and CO2 inline to keep the focus on the livestock. If you go canister, you will want an inline heater like this:
Hydor ETH 300 In-Line External Aquarium Heater, 300w, 5/8" hose https://www.amazon.com/dp/B0002Z7VQE/ref=cm_sw_r_cp_apa_5L3Gzb2FFK2JS
I found that, with my 30 gallon tank build, it was cheaper to turn an old 10 gallon into a sump rather than buy special inline equipment. Maybe you can do the same with an old 5 gallon? There are other added benifits to a sump such as alternative filtration choices, more water volume for stability, refugium, etc.
Either way you go, i would get a co2 reactor. Reduces the size of co2 bubbles going into your tank will make the water clearer.
Gulfstream Tropical AGU00528 Ista Max Mix Co2 Reactor for Aquarium, Medium https://www.amazon.com/dp/B005DGJDXQ/ref=cm_sw_r_cp_apa_js4GzbJCBF4M3
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