SawdustGnome

I have a sponge filter in every tank i own including two that either have a HOB or a Canister for one reason alone. Power outages. Here in Alaska in the dead of winter there are times our power can go out for more than a couple hours (even as long as 3 days a few times) due to a tree falling on a power line in the middle of the woods where it can take the electricity company a while to track it down and repair the damage. In these cases I am able to plug the usb nano air pumps to a power block and i don't have to worry about the beneficial bacteria colonies. The tank will continue to cycle and once the power is back on the colonies that most likely crashed in the HOB and Canister can reestablish on their own without me having to add a bottle from the store. Cheap insurance. Also if you have an air going into a tank you might as well have a sponge filter attached to it in my opinion. I just hide them behind a rock or a piece of drift wood.

They should be fine the only difference between a 20 long and a 29 gal is the 29 gal is 6 inches taller. They tanks have the same length and width (30"x12").

I've only kept salt and pepper cory's so I'll give you my experience with them. I started with 3 in a 29 gal and those three turned into roughly 20 or so that I have now split between two tanks. The grandmother of them all is roughly 2.5 inches and the rest are 2 inches to 1/2 inches in length depending on their age. They have spawned multiply times but now that I have Bristle Nose Plecos in both tanks the eggs do not survive unless I remove them right away. They also live with cherry shrimp which also keep multiplying. I imagine they eat a shrimplet here and there but enough survive to keep the colony going. Having a pile of small rocks and plenty of java moss helps the shrimplets survive. They get a varied diet but I mainly give them Fluval big bites for bottom feeders. I would recommend at least 6 if not 8 to start with. I noticed once the first batch of fry grew up they seemed much happier and more comfortable. They are so fun to watch when they school up in search of food. They reason I suggest these cory's is they are relatively common in LFS's and won't break the bank either. Hope this helps and good luck!

The less I do to my tanks the happier and healthier they seem to be.

I had similar looking structures grow out of wood when I set up a new tank about a year ago. I believe they were some sort of fungus. A year later and they are long gone and never harmed any of the fish, snails or shrimp in the tank including the bristle nose. I wouldn't worry about it.

I have a 29 gal with a Fluval 3.0. It definitely is strong enough. I actually only run it at 50% power. Bently Pasco has a few youtube videos that are very informative covering the Fluval 3.0. I suggest taking a look.

We also only name the ones with big personalities. Our new world cichlids all have names as well as our solid black Betta (Batman). We don't name the danios' and cory cats in our community tank. My wife names them she is much better at finding a name that suits the individual fish.