Ken,
No expert on Goldfishes but have been keeping fishes for a long time. I think your second goldfish is a Ryukin mixed with a Lionhead. Goldfishes can practically eat 24 hrs a day but you should only feed them once or at most twice a day as they also poop a lot and there's where the trouble starts; Nitrogen build up, etc. Each feeding should have the food consumed within 5 minutes. Anything more then that means you could be over feeding. water turns murky, smells and bacteria sets in.
Diseases like "white crown" will start on the Lionheads, scales could "bulge" out of the body, fin and tail will red vein and rot, etc. Have limited number of fishes in your tank as yu have to remember that they will grow bigger.
The algae serves no purpose and should be removed if you want to have clean environment. And above all,
PLEASE DO NOT put in any of those "Bandaraya" (Plecotomas) fish where it is supposed to clean up the waste in the tank(hence the moniker). These guys will attack the more docile fishes given time.
As long as your filter is working, there should be sufficient O2. Dont know if your filter is the overhead type or the underwater corner type. Either way, as long as it is working there is no problem.
Goldfishes can become air breathers for a limited period of time so the best is to have a stand-by battery operated air pump in case of electrical failure.
Another thing; noticed you have gravel at your bottom of the tank for aesthetic reasons. Better to remove them as they trap unfinished food and poop thus leadingto bacteria build up again.
Note that TNB is currently having scheduled maintenance through out the country where power is cut off from 2 to 7 hrs! Check with
www.tnb.com.my to see if your area is affected and at what date.