Problem with surface water tension, I think...

[Chineseghoststory]

Although my salt water nano-tank is just around the corner, I currently have a little tropical tank that is a minbow 5, basicaly just a smaller version of the popular minibow 7 in working respects, and it uses the same Whisper on-the-back filter which I am going to be using in the nano. But I am having what I think may be a problem with the tropical tank that I think I need to resolve before Ihave the same thing going on in the nano.

 

The problem is this: when I look up to the surface of the water through the tank I see small bits of oil, food, maybe some dust and other routine-looking small debris sitting on the surface which the filter is not getting due to how surface tension holds the stuff there. The filter is working as it should and is definitely moving some water in there, it's just not breaking that surface tension and catching that poo or whatever it is. So every day or so I put an airline in, attached to an air pump, and allow it to run for about half an hour, letting the surface tension be broken by the bubbles and allowing the stuff to sink into the tank and then be easily filtered out. The current of the water falling into the tank from the filter is obviously not enough to break this tension on it's own.

 

What is it that causes this? What can be done to prevent it, or should I not worry about it at all? Does this crud on top prevent proper gas exchange? Have I hit already on the best way to deal with it and has anyone else had this problem?

 

Thanks,

 

Jeff

[ajroahkni]

Hey Jeff

 

I'll tell you, if you tell me

 

What is the Chinese Ghost Story?

 

 

John

[Chineseghoststory]

I just thought a story that no one has written yet (any takers?) would theoretically be really cool if , in order to describe the stoyline in the the book, it was called Chineseghost Story. The name also implies the anticipation that one may feel when about to hear a story from a far away land involving things beyond our earthly realm.

 

Believe it or not, I actually got "swordfish" as an e mail address on my server before someone else grabbed it.

Jeff

[ajroahkni]

Okeydokey Jeffie baby...

 

That film you see is actually surface scum, and it is inevitable in your nano. one way to alleviate it is to aerate the surface, via airstone or airified powerhead, however this will lead to salt creep, which is just plain messy. Agitating the surface by aiming your powerhead may do, as will the use of surface skimming contraptions. You could also consider draping a paper towel over the surface and it'll suck up the film. However, the best way to take care of it is to use a shallow bowl to skim it while you do water changes. It's a great indicator that "hey, it's time to do a w/c" because you should be doing approx. 10% w/c per week, and the surface skum usually shows up in 4-5 days.

[lil reef]

If I read this correctly this is a Trop. tank and not your Nano reef. Couldn't you incorporate an airstone or aircurtain across the back to help with the surface agitation? I once had a small terra cotta pot or vase that I had an airstone going to. It looked pretty cool! I had it set at an angle on the bottom with the air bubbles coming out of the top. People always commented on it. I keep the #### out of the gold fish bowl.

[Kapelakin]

What power filter are you using? I'm guessing you have the filter cartridges in it for the FW tank, but when you switch to reef, you won't be running the filter with cartridges, so the water's velocity isn't going to be slowed as much returning to the tank. It will probably break up the scum a bit. You might try taking out the cartridge and making sure the impeller, etc, is really clean, and seeing if that helps break up the surface.

 

I'm running a Penguin mini without a cartridge on a 7 and haven't had any scum problems, FWIW.

[tinyreef]

hagen has recently introduced a surface skimmer (no pers exp tho). or you can keep the water level slightly lower than the return on your hob (or conversely raise your hob's height) so that the return breaks the surface continually.

 

there is a movie called chinese ghost story btw. i assumed that's where your id came from. (jgts you should never assume) it's a cartoon/anime. i saw it when it was originally released overseas in chinese. they released the english version a couple of years back. there are certain cultural aspects that westerners may not understand tho but it doesn't interfere with the storyline.

[sjpresley]

The surface scum is indeed a mixture of stray amino acids and other organic compounds that get caught in the surface tension of the water. The reason such a thing is more common in saltwater tanks than fresh is that O2 saturation in saltwater tanks is much lower than in fresh (i.e., saltwater holds less O2). Increased O2 availability helps in the breakdown of these organic molecules before they accumulate at the water surface. Usually, this film is indicative of relatively low O2 availability.

 

In my nano I have a small power head at the surface creating constant surface aggitation. But the film developed anyway, and fast. After I added a skimmer the film still developed but much more slowly. I finally added an airstone in a back corner, I ran the air pump through a gang valve and put adjusted air flow so that bubbles flow is pretty low in the tank. Salt creep has been minimal and there has been no film in the many months since. I had a concurrent problem with chronic low pH, which is also a sign of low O2. The extra aggitation caused by the bubbles solved both problems.