like you i was corius so i researched and the direct sunlight is like a factory creating algea and the faster the algea grows the more amonia and it breacks the amonia cylce
30 gallon stocking ideas
- Thread starter chubbylizard
- Start date
Algae doesn't make any ammonia, although if you get "green water" it can consume most of the oxygen at night.
This is what I was slowly getting at.
I think you need to do a little more research. Your stock ideas for the 30 are way to lofty. Convicts in a 30 is no good, firemouths in a 30 is no good. Ideally both those fish should be in a 55g min better a 75 especially if there is more then 1. Sounds like you really dont understand the basics yet. I'm not trying to beat you down. I want to help. Do research on the nitrogen cycle and filtration, proper maintenance.
Yeah we were all at this stage at some point in our fishkeeping hobby. One of our staff actually had baby oscar cichlids in a 5gal once, won't mention names! We're all here to help 
I agree with Twentyleagues, having a tank close to a window would not cause the problem. if anything the sunlight would help grow algae that would help eat ammonia.
My tank is situated so that it receives heavy sun early morning, and again in the late afternoon, and its sump is in in longer direct sun as an algae scrubber (set purposely as an algae growth container) and I've never had an ammonia, nitrite spikes, In fact my tank never has measurable nitrate.
Morning
afternoon
The only way I could see direct sun as a problem, would be if it was so intense that it heated the tank too much.
And most convicts can easily take high temps, and nightly drops in temp.
Above my algae scrubber, sitting in direct tropical sun.
Your ammonia spike, is probably because your tank was never properly cycled.
Proper cycling can take 6 to 8 weeks before any amount of un-sacrificial fish should be added.
And referring to the fish I mentioned in an earlier post, Apistos, Rams, or Shell dwellers are more sensitive to degraded water quality than Cons, so adding them to an un-cycled, tank could be a costly disappointment.
Unless your tank is properly and totally cycled, and chemistry is right, you should be surprised if any fish "don't" quickly die.
Cycled means, a large enough population of beneficial bacteria has to be there, to consume the ammonia in fish waste, this does not happen over night, or even in a week or two.
