How I got Rid of Duckweed

Duckweed In A Ten Gallon Aquarium

Goldfish. I bought some feeder goldfish. I quarantined the fish for a month; then, I moved the fish to a tank that had duckweed. When goldfish ate all of the duckweed, I moved the fish to another aquarium — repeating as necessary until the duckweed is gone. Once the indoor duckweed was gone, I moved then outdoors to my 100-gallon stock tank, the source of the infection. The 100-gallon stock tank produced so much duckweed that in the summer, the duckweed would be an inch thick if I didn't scoop it out regularly. It took nearly a year to polish off the duckweed, but they eventually got it.

Feeder Gold Fish

It would help if you fed lightly, or the goldfish may not eat the duckweed as fast as it grows. I now have three sizeable fat goldfish in my stock tank and zero duckweed.

Duckweed Growing  In 110 Gallon Stock Tank With Dwarf Sagittarius

When you buy the feeder goldfish get more than you think you will need. I have used the two times for cleaning up duckweed, and I will lose 2/3 of the fish in quarantine.

Where I live in Tallahassee, FL, feeder fish cost sixteen cents.

Some Thoughts on Aquarium Substrate

Pea Gravel Substrate Outdoors In A Media Mix Pan

Yes, pea gravel will work. I have used it, and there is a local fish store in my area that uses it exclusively. It usually has lots of dust mixed in, and I find it challenging to wash. Nowadays, I don't rinse it. The rock dust will settle to the bottom of the tank or get taken out by filters. It is a bit hard to get plants to stay down until they get some good root growth.

I have also used Black Diamond blasting grit. It works great, but it is nasty right out of the bag and, you will need to wash it first. I have had it in an aquarium with a bunch of cories for several years, and despite what the internet will tell you, they have not ground their barbles off. I have watched them bury their nose in it up to their eyes. It would be best if you looked for the coarser grit size.

I also use pool filter sand. I'm not crazy about the color I can get here, but it works well, and it's cheap. The price is reasonable enough that when I reset an aquarium, I use new sand. My plants seem to love it, and I don't wash it.

Colored aquarium gravel is expensive, and the lower cost gravel will slowly lose it a coating. I have used several brands over the years. The only ones I liked were the natural colored gravels and some made from what looked like black glass. I can't find the glass gravel sold anywhere. It was smooth with no sharp edges, was easy to clean, and my plants grow well in filter sand.

I have never used any of the fancy substrates that are made for plants and probably never will. My plants do just fine without them.

I have used dirt; it grows plants like crazy, but it can be messy. I love my cories, but they like to dig, and sooner or later, they will get through the top layer of sand and into the dirt. Forget bristle nose or any fish that likes to dig. They will keep the soil stirred up and clog the filters until the filters remove all the dirt.

Outdoor Plants In My Stock Tanks - Above Ground Ponds

110 Gallon Stocktank - Above Ground Pond With Guppies, Mystery Snails, and Platies

I live in Tallahassee FL. I have three outdoor year-round Stock tanks. I have also used various other containers; Aquariums, Concrete Mixing Tubs, wading pools, and stock tanks. I have plants that have survived air temperatures well below freezing. I once had more than an inch of ice for a few days.

Plants that have worked for me so far are dwarf Sagittarius, duckweed, anacharis, and Amazon Frogbit.

Dwarf Sagittarius, will grow in any tank I have but works best if it has a little substrate. It grows to the top of the water no matter how deep blooms and will cover the bottom of whatever you put it in.

Duckweed is, well duckweed. It will cover the top of the outdoor tanks. I have had it two inches thick and scooped it out by the hand full. I finally got rid of it everywhere by adding some feeder goldfish. It took them a while, but they ate all of the duckweed.

Anacharis is picky about where it grows. I have some containers where it slowly dies and others where it grows but not what I would call well. I have one 100 gallon stock tank that I routinely pull out a bucket full. It grows slower in cool temperatures, but it still thrives in winter. It grows like crazy in the summer and blooms.

Amazon Frogbit did well for me year-round. It grew huge outside and had lots of flowers. Unfortunately, armyworms decided it was good to eat, and I could not pick them off fast enough to save it. My guppies would devour the caterpillars, even picking apar the larger ones.

Crypts grow very well in summer but will not survive our mild winters.

Amazon swords don't survive the winter but grow well in summer.

A few days ago, I added some huge Anubis I removed from a tank I had indoors because they were so big they were growing out the top of my aquarium. 

Undergravel Filter Good or Bad?

I used under gravel filters for years with no issues other than fish that dig. I got out of the hobby for several years. When I came back aquariums on the internet had exploded.  Many things had changed. One of these changes was how everyone hates under gravel filters. In my opinion, this is primarily due to marketing. 

Marketing is the same thing that drives the hang on back filter systems that use cartridges. The primary reason behind these is the need for companies to get repeat sales.  If you are using under gravel filters and don't break them, they get one sale. 

I have sponges, hang on back filters, and canisters currently in use. I even have a few box filters. I have experimented with every sort of filter I can find and have made or modified a few of them. The only ones I really like are the sponges.

I think for me the air driven filters are the best. I live in hurricane country. During a hurricane, I can lose power for a week or two at a time. With a box of D cell batteries and a few battery powered air pumps, I can keep my filters running. Currently, I have sponge filters in all my aquariums in addition to the other filters that I have.  This more sponges than I need to run the aquarium so I can keep my biological filters going when the power goes off. 

I think that in the future I will be switching all of my aquariums that have substrate to under gravel filters. I will keep sponges for bare tanks and new aquariums. 

Watch this video. Cory makes a lot of excellent points.