Originally Posted by Hallyx
I'm new to this game and have never heard of either of these. Can you direct me to more information?
Well, umm... I can give you the links to what I use, but I doubt they would be too much help.
The porous balls I use are these:
I use the soft water type S size for bettas - it keeps the ph from rising, and bettas like low ph. It has 1620 square meters of "surface" per liter of pellets... It can really help to keep a good and steady cycle in a small tank. (I use a different type of their product - monoballs - for my goldfish, minnow, and medaka+shrimp tanks.)
The gel sponge is this:
I just cut what size I need from it.
I think that the Eheim filter balls and the like are similar to the balls I use, but I don't know about the sponges... I really like the gel type as they can be used repeatedly with washing instead of falling apart and needing to be thrown away like the "wool" types.
I've never had space for an HOB before, but now I do. Do they make more noise than a fully-submerged cartridge type?
I'll be honest and say that I only have one HOB... It is about the same in noise level as the two fully submerged filters I have. I find it is a lot easier to reduce surface agitation with the HOB... It was a huge pain to do so with the submerged filter in my female's tank.
The quietest, by far, is an external filter, but that is kind of overkill for a 2.5 gallon.
The biggest plus for an HOB is that there is usually a lot of space to put media, and it isn't as picky about shapes. It is usually just a "cup" to put media in. Water is pulled up into the filter on one side, and flows out of a lowered point on the other side. You can do all kinds of DIY stuff with a really cheap HOB to make it be a really good filter. I cut up plastic cups to make a sort of water "maze" so that it has to flow through a bunch of filter balls and then the gel sponge before it can go back into the tank.
My limited space requires that both be show tanks. I originally wanted to place the filter and heater in a separate utility tank between the show tanks--output into both, then siphon back into the sump. A pond professional friend advises against this. He says it's finicky and can be quite a mess. My small experiments in almost equal water level siphoning bear this out. It's not really like a sump or like a Betta barracks. I had hoped someone here with more experience might have been able to advise me otherwise.
Having two tanks going into one filter is a bad idea for several reasons.
Let's say you get it set up and running well. What happens if a chunk of gravel or even a big piece of plant material is sucked into one of the pumps? Or even if one of them slows just a bit more than the others? Water ends up going out and not coming back in... You could easily end up with something overflowing. At worst, you end up with an emptying tank and dead fish.
Not to mention spreading illness...
Even with a single tank and single filter tank, you have to be really careful and set the tank water levels low to make sure that if something fails you don't have and serious problems... With two you don't have as much leeway.
Your suggestion--lots of filter area---is the simplest and most reliable method. The only drawback seems to be the tank volume occupied by filters, heaters and foam.
For the most tank space in a small tank, the easiest has to be an HOB. It will actually increase the water volume by a small amount, while an internal filter displaces water and reduces it slightly.
The best would, of course, be an external filter... But from what I hear, they don't sell small ones in the US. If I ever put something more demanding than a betta in my smallest tank (shrimp or the like) I will probably pick a small one up as they are available here for very small size tanks.
[quote ]Thanks, Tamyu, yours have been the most helpful suggestions I've received so far.[/quote]
I am really glad I could help in some way. I am actually fairly new to the betta world, but have other fish, so know a bit about filters and the like.