promoting algae growth

I'd like to do what most aquarists would never want to do, promote algae. And I'd like to do this without harming the animals in my tanks (in my case crayfish). I think adding phosphate might do the trick. Where can I get pure phosphate fertilizer to try this? I'd rather not add nitrates and potassium for now.

Most home improvement stores and nurseries will have phosphate fertilizers, usually pretty cheap. Rock phosphate has no N or K, but may have associated acids that will mess up your pH. Bone meal has a little N, but is more alkaline, which most algae prefer. It also provides Ca, which will probably benefit your crays.

I'd recommend buying a marimo ball, which is made of cladophora algae. This algae is very persistant, growing on everything and refusing to die. It'd be perfect for someone trying to culture algae.

I had the idea to experiment with the stuff myself, and about a year or so ago thought it would be a good idea to cover my gravel with it, since I had so much. Here's the result:



Before and after: http://img.photobuck...oreandafter.jpg

You can see I had a CO2 diffuser in the tank at that time. It was linked to a 2 liter that contained yeast and sugar in aqueous solution. I have since removed that diffuser and have found no slowing to the growth of the cladophora. It's been my most persistant plant species in all the time I've had my tank. Substrate has changed, water conditions have changed, other plants have come and go, but the cladophora has always been here. Range of pH: 7 to 8.3. Range of degrees of hardness: 6 to 20. Range of water temperatures: 60 to 85 Fahrenheit. Range of lighting: low to high. Range of substrates: pure gravel, gravel with crushed coral, gravel with kitty litter, and pure kitty litter. Cladophora's always hung on. I'm sure you could culture cladophora quite easily.

Edited by EricaWieser, 01 May 2011 - 12:18 PM.

Why not potassium or nitrate?

I'm sure you've already thought of this, but you probably want to slap some extra lighting on the tank.

I'm curious - what type of algae are you trying to grow? Unicellular (green water)? Filamentous for the crays to chew on?

"Why not potassium and nitrate?"

No strong reason. I know Phosphates are a top thing that promotes algae, so I'd like to add them and at the same time limit what I'm adding to the tank. I've heard that high nigrate levels might not be good, so why add them if you don't have too.

As for the type of algae, I don't think it really matters, just the normal stuff that always shows up. The reason for trying to promote algae is that in tanks where algae is abundant, the crayfish seem to have more natural colors. The connection is not certain yet, but I'm trying to figure it out. A big problem with captive crayfish is that they turn varying degrees of blue (unnatural colors). I recently thought about feeding them algae wafers, but the wafers in the pet stores seem like they contain only a small percentage of algae. I don't even know why they call them algae wafers. I recently bought a bottle of spirulina pills to feed them. They are 100% algae, but the crayfish don't find them appetizing. The crayfish definitely eat the naturally grown live algae in the tanks. Most of my tanks (50+) have varying degrees of algal growth, but a couple of the tanks are totally disgusting, with about a half inch pile of fallen algae on the bottom and glass covered. In those tanks, the crayfish have notably natural colors.

Well, potassium phosphate is pretty readily available if you google "aquarium fertilizer." Probably could be had cheaper other ways too. Avoiding nitrate may be wise. In general a high accumulation of dissolved solids isn't the best thing for freshwater fish, and nitrate tends to accumulate anyway as I'm sure you know, but even a small KH2PO4 supplement may well spur enough plant growth to deplete the nitrates. Some algaes will still grow in water with no detectable nitrate, but they won't be as nutritious as food, since they need some form of nitrogen to make protein. I'm not usually a big believer in water testing, but before I started a fertilization project I'd want to know what I was starting with. I'd probably target about 40 ppm nitrate. I wouldn't bother testing for the other two though.

I would also second the recommendation of introducing an algae that will accept the existing conditions, although Marimo balls are an unnecessarily expensive way to go about it. Just grab a variety of different-looking wads of green goo from local waterways and throw them in and I guarantee one of them will grow.

...Marimo balls are an unnecessarily expensive way to go about it...

I agree with most of what you said, and would like to chip in that personally I wouldn't go above 30 ppm nitrate.
I feed my fish two to three times a day and that takes care of all my fertilization concerns; the plants and algae grow very healthily.

Also, marimo balls are going for $4-$5 total on ebay including shipping. Link: http://shop.ebay.com...4&_sop=15&_sc=1

Edited by EricaWieser, 02 May 2011 - 09:42 PM.

I sell Yakato balls on my website for $10 plus shipping - more expensive but 4 times more effective. Don't forget to check out my solar pond filter too!

I recently thought about feeding them algae wafers, but the wafers in the pet stores seem like they contain only a small percentage of algae. I don't even know why they call them algae wafers. I recently bought a bottle of spirulina pills to feed them. They are 100% algae, but the crayfish don't find them appetizing. The crayfish definitely eat the naturally grown live algae in the tanks.

Have you tried feeding them something like spinach?

Have you tried feeding them something like spinach?

I've thought about that, but it seems like a bit of a pain. It floats, so either I have to cook it, or have to use clips or weights.

I'm currently also trying live aquatic plants, but so far they seem to only nibble at them a bit. I've tried Bacopa monnieri and Lugwigia octovalvis.

I'm also thinking about dried tree leaves, but too many of them turn the water brown. They definitely like munching on willow leaves.

Unless you've also got lush plant growth going in the tank, turning up the lights ought to do the trick without doing much of anything else. You never know what kind of algae you're going to get though, unless you see the tank with something you don't find objectionable. If you wind up with a bunch of green spot algae and black brush, it'll look awful and just about nothing will eat it.

The problem with trying to grow a nutritious and delicious algae or plant WITH your herbivores is that you're selecting (ecologically) against it. Be they fish, crays, daphnia or rotifers, whatever algae they DONT like to eat is what ends up growing best. So in the long run it works out better to grow your food plants in a separate container and feed them to the animals as needed.