How Green is My Water
December 24, 2010 9:07 AM   Subscribe

We have a ten gallon tank and a goldfish, Monster Truck, the best goldfish a girl could win at a county fair Monster Truck II the best replacement goldfish for the best goldfish a girl could win at a county fair. We also have an impressive amount of algae.

The tank has rocks on the bottom and a water filter with a new replaceable filter and a UV light we leave on during the day and shut off at night. The tank was in sort of direct sunlight for a few hours a day and developed a bad algae problem over the course of several weeks. I cleaned the tank and the rocks and fake plants as best I could with water, but did not want to use anything stronger on the poor little guy's home. Apparently we just made it mad because within a week in a new spot, out of direct sunlight, the algae was back stronger than ever.

I even got Monster Truck the R2 Fish Training School for Fishmas but we won't be able to see him jump through his tiny hoops!

So my questions: is the algae bad for the fish? How do I get rid of it? How can I prevent it from coming back?
posted by shothotbot to Pets & Animals (12 answers total) 1 user marked this as a favorite
The algae isn't bad for the fish; it's just a plant. The issue is more with 1. being able to see him, and 2. sometimes heavy algae growth is a sign of an underlying issue wherein you're getting too high levels of nitrites and nitrates in your water. You can take a sample of your water to a Petco and they will do a free water test for you (at least, they used to when I worked there) and they can tell you if your nitrite/nitrate/ammonia levels are in a dangerous range.

If all's well, it could just be the light; try replacing the bulb in your light. As bulbs age they change in wavelength and can cause more algae.

AlgaeFix or other water additives can help keep the algae in check.

You might also consider adding a couple of Mystery Snails or Ramshorn snails; they will eat algae and leave little clean trails where they've grazed. This makes it easier for you to come along and scrub it off.

And finally, the main thing ya gotta do, what we always have to do for fishtanks, is to clean it. There's magnetic algae scrubbers that make it easy to do a quick job without getting too wet, and as you vacuum-siphon the rocks with your regular water change (you do regular water changes right?) you'll get the algae off the rocks that way and also remove wastes that are fertilizing the algae.
posted by The otter lady at 9:25 AM on December 24, 2010 [2 favorites]

I used to clean my goldfish tank with non-iodized salt. it is cheap and nontoxic - just rinse everything really well - and it really scrubs all the crap off of everything.
posted by toodleydoodley at 10:05 AM on December 24, 2010

The magnetic algae scrubbers mentioned above are amazing (this isn't the one I have, I actually picked one up for $3 at Walmart). I have a tank that doesn't produce too much algae (a few African Dwarf frogs and a few snails) but some highly ineffective snails that will clean the algae off of the decorations but not the tank walls. A few swipes of the magnetic cleaner takes care of it, and the entire process of cleaning the tank walls and rinsing off the cleaner takes less than 5 minutes.
posted by kro at 11:04 AM on December 24, 2010

Algae in the tank usually is more of an aesthetic problem than an issue for the fish directly. It does reflect too much light and or nutrients for the algae to feed off of, which usually means you're overfeeding your fish and or not doing enough water changes. If you want to get a handle on this, scrub the tank, reduce the amount of light on it, cut back your feedings, and increase the frequency and volume of water changes. If that doesn't work, you can consider adding a variety of potential algae eating critters/fish to the tank.
posted by drpynchon at 12:29 PM on December 24, 2010

Nthing magnetic scrubbers for interim cleanings. I sandwich a thin aquarium sponge between the inside of the tank and the inner magnet, then rinse all the accumulated algae down the sink. The sponge collects algae better than the lining of the scrubber does on its own and if the sponge gets hopelessly fouled, you can swap it for a clean one.

Anything that can be removed from the tank can be scrubbed down with tap water and a plastic kitchen scrubbie. Make sure the kitchen scrubbie is reserved for fish use only and never comes into contact with detergent or soap (I keep my tank cleaning equipment in a cut-down plastic gallon water jug marked "Fish Use Only" and store them well away from the sink so they don't get borrowed by accident). You can also put most types of plastic or resin decor into a bucket with some tap water & a bit of bleach, just make sure to rinse the items thoroughly with water and declorinator before returning it to the tank (tip: if you can still smell the bleach on the item, it hasn't been rinsed anywhere near enough).

A good part of the problem you are having stems from the small size of the tank and the species of its occupant. It's much more difficult to keep the chemistry of a small tank stable compared to a larger volume of water. Monster Truck, like all goldfish, releases a tremendous amount of poop, which quickly fouls the small amount of water and overwhelms the filter all while fertilizing the algae growth. To continue to keep him in there, you'll want to step up the frequency of water changes and filtration material swaps. He'd really be better off in a tank at least twice that size, though.
posted by jamaro at 12:35 PM on December 24, 2010 [1 favorite]

Goldfish are notoriously dirty (read: poopy) fish. Make sure you're not feeding it too much. No more than it can eat in a few minutes once or twice a day. Try not to let any food accumulate uneaten, it will contribute to nitrates. Minimize the light for a while, that should make it harder for algae to grow. A new bulb, as mentioned above, can make a world of difference.

Also, if you can increase the number of water changes or the volume of water changes you do, that would help clear out the system. Make sure you're cleaning the gravel to get out the gunk that seeps in. In a smaller tank, small (25% or less) frequent (at least weekly) water changes are best.

And algae eating creatures can be fun roommates for your goldfish. Try snails or crabs. The trumpet snails are fantastic, and once you have a few, you'll notice they quickly reproduce to colonize the gravel of your tank. Built in cleaning crew! Plecostemous (sucker-fish) are great, but can quickly grow to monster sizes. I had one that topped out at a foot and a half. Make sure you buy a type that stays small. Some will stay under four inches and they love to eat the algae. You'd need a small piece of driftwood for it to munch on too to be truly happy.

Good luck. Sometimes an algae battle takes weeks and true determination to clear out, but its a great hobby and don't let the green evil discourage you.
posted by gilsonal at 1:16 PM on December 24, 2010

Well I know everyone is going to yell at me, but, I had fresh water tanks for many decades. I cleaned them with bleach. Yup, bleach. Everyone yell now. I soaked the all of the plastic stuff (not the porous rocks) and occasionally the tank with a strong dilution of laundry bleach. Rinse well, then rinse again. It killed the algae and cleaned the tank. I never had a problem.
posted by fifilaru at 2:02 PM on December 24, 2010

You are feeding your fish too much. I don't know how much your are feeding your fish, but I can almost guarantee that it is too much. Feed half as much as what you are feeding now.

Also, change a couple of gallons of water once a week (maybe twice a week until you get the algae situation under control). It'll keep the levels of dissolved fish urine and feces to a minimum, which deprives the algae of some of its food.

Get one of those magnetic algae scrubbers; as mentioned above, they do wonders.

Do not get a plecostemus or "algae eater." For one thing, they prefer water a lot warmer than goldfish like. For another thing, they will often (though not always) come to prefer the sucking your goldfish's healthy slime coat right off of his skin to actually eating algae; this is no help at all with the algae situation and certainly no good for the goldfish. There are a few types of creatures that can coexist peacefully with goldfish, but I'd recommend against using them in a 10-gallon tank (one of them, which I've sold as an "algae shark," gets really big, and other, the apple snail, can die and pollute a 10-gallon tank so quickly that the water will be lethally poisonous to your goldfish before you even notice the snail is dead).
posted by infinitywaltz at 4:17 PM on December 24, 2010 [1 favorite]

Response by poster: We are trying to be careful about how much we feed him, we give him as much as he will eat in a minute or so. I like the snail idea if he can keep the place tidy. Do you get them at the pet store?
posted by shothotbot at 7:18 PM on December 24, 2010

You can get apple snails at the pet store; you want to get the big golden orange ones. They won't really keep the place clean on their own, but once the algae situation is somewhat under control they can sort of help keep it in check, if that makes sense.
posted by infinitywaltz at 9:42 PM on December 24, 2010

I wouldn't go with an apple snail, actually -- snails are kind of poopy animals themselves, and that's the last thing you need to put in your tank. As jamaro said, your tank is already too small and probably underfiltered to handle a goldfish, which can produce a third of its body weight in waste every day; you don't need to add another waste-producer to a system that's probably already under strain.

You might find this article on algae in goldfish tanks helpful. I also strongly recommend learning about the Nitrogen Cycle (1, 2) and how to stabilize your tank's water quality.

I would get a water testing kit from your pet store (drops-based, not the little paper strips, which are much less accurate) and find out what exactly is going on in your tank water. From there, you might need to do more water changes, get a stronger filter (scroll down here), and ultimately upgrade your tank if at all possible.
posted by bettafish at 11:49 AM on December 25, 2010

While it's usually a truism that no matter how big your tank is, it's always too small, that's debatable... because it really depends on how big Monster Truck II is, which you don't say. The rule of thumb is, 1 inch of fish per gallon of water for tropical fish, twice that for goldfish (which are indeed very messy animals). So if MT2 is under five inches long*, really a 10-gallon isn't too small, provided you A. have a decent filter and B. Keep the tank clean (inc. not overfeeding, and doing water changes/gravel vacuuming.) Can you tell us more about your filter? Like Gallons Per Hour, and types of filtration (biological, chemical, mechanical)? I know you said "with a replacable filter" which is a good start but if you can tell us more about it we can provide more help.

*As the fish grows, you should provide a larger tank, of course... it's not true that fish stay small if they're kept in small tanks; they just get to a certain size, and then stop growing because they're dead.
posted by The otter lady at 1:10 PM on December 25, 2010

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