Quite agreeable. Divemaster, keep this in mind.
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well I don't think that more aeration could hurt. I am getting the sponge filter just to over filter as well not just for the air.
*** if you double or triple the DO concentration in the water that is fed into your main filter, it is likely you will have doubled or tripled your MAIN filter's capacity. If not, you at least very significantly increased it. Did you read the last link? This article may seem hard to digest but forget all the numbers and the equations and science language, just focus on the conclusions in bold. This article is the best one IMO, written by a waste-water-treatment-lab director of one GB University, aka dw1305 on Planet Catfish.
After reading those I think I should get either 2 airstones ...
*** As that article says, membrane diffusers are better than ceramic.
or a powerhead in addition to the sponge filter. I do however have a limited budget and cant be spending more than $50 for a powerhead.
*** I'd ditch the sponge filter and get a powerhead . E.g., from petmountain these two are $16 and $18:
1. Marineland Maxi Jet Water Pump and Powerhead: : Maxi Jet 1200 - (Max Head 6 Feet) Sku: M90512
URL:
http://www.petmountain.com/show_product/11442-526521
SKU: 526521-ML90512-M90512
2. Marineland Maxi Jet Water Pump and Powerhead: : Maxi Jet 900 - (Max Head 5 Feet) Sku: M90511
URL:
http://www.petmountain.com/show_product/11442-526520
SKU: 526520-ML90511-M90511
I also have a planted 30 tall (which after reading those sounds like a terrible combo) which I will need to be getting some more aeration for as well.
*** Please read that article - it addresses this superbly too.
For either tank: what additional aeration would you recommend getting and how much?
*** There is really no recipe. A filter properly sized for your tank volume or oversized and properly used plus a bubbler=diffuser or a powerhead are usually plenty.