Your filter should do the job but I have had great success with AquaClear filters, should you need a change. Fluval Cannister filters are also a favorite of mine if you need an option.
With the location and intensity of your lights, you may have a problem growing the carpeting plants or grasses. These are normally planted in the front of the tank and need high lighting. I believe your lights are located in the back. There may not be enough light reaching the front. There may also be an issue with bringing out the color of you fish. Nicrew LED lights have been great for me. They are bright and have adjustable dimming. They are designed to sit on top of a tank (usually with a glass cover) and can be positioned for the best viewing angle and plant growing. It looks to me that your existing lighting may be more favorable for broad leaved plants that don't require a lot of light. Anubia, Java Fern and Java Moss come to mind. When looking for plants, look for low to moderate light requirements and, to make them easier to plant, the ones I mentioned can be tied or glued to rocks or wood. Also, when buying plants, try to get those with roots in plastic pots rather than loose or banded with weight strips. The roots help to anchor them until they are established.
Next up, your sand or gravel. The Fluval you have should be OK with rooted plants provided you have enough depth to hold the roots down. Pea or coarse gravel is going to trap debris and leftover food making water changes more important. And yes, you should be doing regular water changes. Nothing kills fish more than polluted water (except for chlorinated water that has not be aged, treated or brought to the right temperature).
Adding water back to cover evaporation is concentrating the bad stuff that kills fish. If you haven't experienced this, you have been very lucky.
Painting your room shouldn't be a problem with a cover tank and good ventilation. Latex paint would be better and easier to clean up. Put plastic over the tank during painting.
Your tank and plants should be ready for fish in 4 to 6 weeks. I want to remind you of the fishless cycling with a few drops of pure ammonia each day. The ammonia replicates what fish and fish food produce and is easier to control. Please, go to Amazon and, $12.72, purchase this:
https://www.amazon.com/dp/B007R52CZ2/?tag=ff0d01-20
Without the hassle of test vial, counting drops, trying to compare colors and inaccuracy of testing for "free ammonia", for a year, it will give you a visual for ammonia. You only have to test for nitrite, nitrate and the others.
!
. Only one piece is necessary for coarse filtration as it comes into the filter. The rest should be sponge material to do the real work of clearing water in a cycling aquarium through good bacteria that becomes dominant in time. In all fairness, you could be talking about a totally different problem.
I can't wait to hear how it goes when it's time to remove it! I'm still rinsing my ick daily. 
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