Question About Filtration

[DianaFaye]

Hoping you guys can shed a little light on this for me. I had posted on another forum about plans for my 40g breeder, and one thing led to another and now I'm all kinds of confused.
 
I currently have an AquaClear 30 filter that I originally had gotten for a previous tank. I was intending on getting another AC 20, or trying to swap out the one I have for an AC 50 (the result being, either way, for the filtration to cover 50g). I thought that this was sufficient for my new 40g and would give me a little extra filtration, but then someone had posted and informed me that I would need to add an AC 70 or higher in addition to what I have now. They told me that the AC 30 is really only suitable for a 15g tank. They did try to help me out with info on GPH but I'm still confused.
 
Also, if it makes any difference, I've been toying w/ AqAdvisor to plan out my stock, and I'm currently in the ballpark of 2 dwarf gouramis (or 1 moonlight gourami), 10 cardinal tetras, 10 harlequin rasboras, and 4 emerald green corys. According to that site (assuming I added an AC 20 to my AC 30), the tank would be sufficiently stocked and bioload still within range for filtration. 
 
I'd love to get the best of everything, but money is tight and I do have other equipment that I need to get, not including decor and fish. Am I safe with what I have for that stocking idea, or am I ill prepared?

 

[attibones]

Ideally you should be looking at the gallons per your turnover rate. For your aquaclear 30, the listed gph is 150. You should aim for at least eight times your volume in gph (it's best to find 10 times your volume), which means you need anywhere from 320 to 400 gallons per your turnover. This number is typically listed on the box (but the label is usually pretty much higher than actual gph). Does that make sense?

Of course, if you combined your current filter with an AC 20, which has a listed gph of 100, you'd only have 250, gph turnover. However, if you got the AC 50, with a listed gph of 300, your total gph would be 450, which is sufficient. Remember that you can never over filter.

By the way, I'm assuming you are talking about the stocking-calculator-site-which-must-not-be-named. Please do not listen to the numbers provided. They really do not take many things into consideration. I'd also say your stock is pretty heavy for a 40 gallon, what with two mid level schooling species, but I may be wrong. You'd also do better with more cories.

 

[TwoTankAmin]

AC 20  = 100gph
AC 30  = 150 gph
AC 50  = 200 gph
AC 70  = 300 gph
AC 110 = 500 goh
 
I have about 25 running AquaClears - all of the sizes. Only the 110 is currently not in use.
 
On my 40 breeder tank I have an AC 50 and 2 x 30 for a total of 500 gph max. They do not run at those rates with media in them. I used that combo because I had those sizes on hand. Buying from scratch I would use a 50 and a 70.