I'm in a similar situation right now. I was pretty ill (read: could barely get out of bed and needed a couple hospital visits) for the better part of four months. Wasn't able to do any tank maintenance in that time. When I finally got to look at my tank again, everything was completely covered in a thick mat of dark green algae and all my plants were dead.
Looking at the tank, I couldn't see any signs of life beyond the algae, so I didn't prioritize cleaning it. It was just such a depressing prospect in my mind that I wasn't quite ready to face it yet. Well, I finally decided to start tackling it this weekend. And to my surprise I seem to still have at least three cory cats and four tetras still hanging on! (Now I feel supremely guilty for not attending to the tank sooner.)
Being that the tank isn't as barren as I thought it was, I didn't want to get too aggressive with the water changes and overall cleaning.
I tried to remove some of the thick mats of algae from the sides of the tank and did about a 15% water change on the first day.
I've also added a couple of Java fern and two anubias to the tank. (Hoping they'll start sucking up some of the nutrients that the algae has been feasting on these last months.)
Changed half my filter media and did a 5% water change the second day.
From here on out, I'm planning on doing daily small (~5%) water changes. As well as trying to add a bunch more plants. Hornwort, by all accounts, grows relatively fast, so I'm thinking that may be my next addition. I'll also try to remove as much of the algae mat as possible. My lights are also about a year old at this point, so I'll be switching those out for new ones within the next week.
Unfortunately I have no idea what my water parameters look like at the moment as I lent my test kit to a friend who was setting up a tank. I didn't think that I had any immediate use for it as I figured I'd just be breaking down my current tank and starting over, not trying to resuscitate it! I suspect that they must be fairly terrible though as the tank had gone for almost half a year with no maintenance.
Once I can get my test kit back and get a better idea of the water parameters, I may consider adding a bristlenose pleco. I've been told that they're pretty good about sticking to eating algae and not going after slime coats or getting too aggressive as they age and I love plecos anyway, so a bristlenose seemed like a solid choice to me. (Tank is 85 gallons so bristlenose should not outgrow it.)
Hoping that if I can stay on top of the cleaning and water changes and get enough plants and some decent lighting going on then I can bring things back under control. I'm sorry that I let the tank go as much as I did, but hopefully the situation is still salvageable. Wish me luck! And good luck with your tank clean-up as well!
