Orandas: Filtration & Gallons Per Fish

Question
Hello Darryl.  I am a new hobbyist (2 months in) and I only keep Oranda goldfish.  I do not have intentions to keep any other types of fish.  I have a 29 gallon tank, a 55 gallon tank, a 100 gallon tank, and one 20 gallon quarantine/hospital tank.  All of my tanks are cycled, but at present, only my 55 gallon tank has fish in it.  I maintain cycling on the other tanks using fishless cycling procedures.  The tanks contain 1.5" of gravel and minimal silk plant decor.  I am not set up to manage live plants.

My 55 gallon tank has 5 orandas in it.  One is 5.5", two are 4.5", and two are 3.5.  So far, the 55 gallon tank and filtration is handling them fine and provides enough room for all of them to swim.  

I have encountered several conflicting accounts of how many gallons of water are needed per fish.  My understanding is that when fully grown, Orandas typically reach 7-8". Assuming that fully grown Orandas are 8", how many gallons of water are needed for each?  

Currently, I am not in a position to set up a Fluval or other cannister filters so I have been using hang-on power filters instead.  Here's what I am running:

1.  20 Gal Quarantine/Hospital Tank:  1 each Aqua Clear 30
2.  29 Gal Tank:  2 each Aqua Clear 30's  
3.  55 Gal Tank:  2 each Aqua Clear 70's
4.  100 Gal Tank: 2 each Penguin Biowheel 350

Additionally, each tank contains an 18" Bubble Bar for aeration, except the 100 gallon which contains two of these.

Do you think I have enough filtration and aeration for these tank sizes and the type of fish I keep?  How does one determine filtration & aeration needs, especially for fancy goldfish that are messy?  What guidelines do I follow to establish whether I need more filtration or if I have too much filtration?  

I have a very good handle on water quality as I consistently test the water parameters every three days and also perform gravel cleaning and water changes (30-50% depending on need) every week.  But I'd like to make sure that I also provide my fish with enough gallons per fish and enough filtration and aeration to keep them healthy.

Answer
Hey,

You're perfect on filtration. Way over powered on filtration, actually. The AquaClear 70 can handle something like 60 gallons of water with supreme confidence, and upto 80 gallons with average upkeep. Thats each unit. you have two? that's insanely over powered. Not that the fish care, but your power bill might! If you are happy with your water quality, then keep at it. Use your best judgement.

As for gallonage: here's my rule. 3-4 gallons per inch on goldfish. With fancies, i go with 4. Comets get 3. In a 55 gallon, you'll get about 3 adult fish comfortably. Perhaps 4 with your filtration, by my standards anyway.

Seems like you've got all your fish in a line, so I'll leave you with just opinion. You've got facts under your thumb thus far, so I'll leave you to make your best judgement call from here :)

happy fishing.