Originally Posted by Ouch
What I would recommend is rather than a filter is you purchase a water pump, or pond pump (not air pump or bubbler). To oxygenate a goldfish tank you need heavy surface action, you'd need one about 500gph. If you have a lid on the tank remove it. This way your tank will be oxygenated and should grow algae no problem provided it's cycled.
If you have ammonia and nitrite, then what is your source of nitrate? Normally only see high nitrates in cycled tanks, unless it's in your tap water.
I think it's fully cycled, it's been set up a few months with long used filters, I only recently upgraded to the bigger filter. Everything else has been in the tank a while and it seems pretty oxygenated. The covers are rather shabby so there's lot of open space and I keep the water table a touch low so there is some surface disruption. I'm just hoping for a full out bloom xD
The 20 was fully cycled before I moved to the 55 for a while. I've just never had the tank tested with a real testing kit to get numbers, just taken it to petco and told it was in the "safe" or "good" range.