Brown Algae

Brown algae is a type of diatom which gets energy via photosynthesis or through chemical means. It, like true algae, is generally triggered by an imbalance of lights or nutrients in the aquarium.  To try and work out which one of these may be the issue in your set up please could you describe:
* your lighting schedule
* water change schedule
* any dosing of fertilisers, liquid carbon etc
* water test results

Wiping it off the tank and decor works, along with water changes, and it would be good to get to the bottom of the problem.
Brown diatoms are quite common in new set ups.
How long have you had your tan set up? Is the this one you've recently added the angel fish to? Sorry I can;t remember, but was it fully cycled prior to adding the fish?
What are the water parameter and test results?
Basically, if you can provide as much information as possible we will try to provide advice, although this may be a bit of an issue with a ne set up/recent addition of fish, that will settle with tank maintenance and regular water changes.

The tank may still be considered relatively new, rather than fully mature. The addition of the angels recently will also have increased the amount of waste/ammonia in the tank, if only temporarily.

Did MA give you values for your water parameters? Or just say it was OK? I would suggest getting a test kit yourself as ideally you should be testing the water every week to monitor it. I use the API freshwater master test kit. This can test the pH, ammonia, nitrite and nitrate. When I first set up a tank & introduce fish I tend to test at least twice a week - once just before a water change (to see if anything has built up over the week), and again the following day. This can also help you to understand if the amount of water being changed is enough.

Is your tank very heavily planted? 8 hours of light a day is a lot. If your tank is planted heavily enough to require and 8 hour photo-period I would expect the plants to be out-competing the alga for nutrients. Do you add any extra plant fertilisers or anything? I'd recommend reducing the amount of time that you have your tank lights on to perhaps only 4 hours for now. The lighting/bulb itself is fine.

How much do you feed your fish? Do they eat everything within a short amount of time (say less than a minute) or is there any food left for them to graze on later? I'm wondering if excess food may be adding ammonia to your tank, which will no be helpful. Again, being able to test the water will answer this one.

A reduction in the light, along with regular water testing, wiping the diatoms off the surfaces, and a minimum of 25% water change each week should help to reduce your problem. If you keep us updated on hat has been done, and the progress being made with the diatom problem, then it will help us to work out exactly wha the problem is and how to fix it.

Sorry it's such a long message, but I hope it helps.