Freshwater clams and algae effectiveness??

[krissyfish20]

I'm just wondering if anyone has had any good experience with freshwater clams/mussels and their ability to clear algae. I work at the uni, and some of our big zooplankton(daphnia to be exact) tanks are so overrun with algae (it all started during the extreme heat at the beginning of the summer and with us not innoculating with daphnia right away) that now we cannot culture any of the zooplankton. we have been filtering out half the water in the tanks and then back in to clear some of the algae (they just have to be a little less green, not completely clear), but the filter is 100bucks a week to rent and the filter bags are 26 bucks each and we need 28 filters. I thought that clams might be effecient enough if we put a number of them in each tanks and left them. does anyone know how efficient they are?? I've heard they're good!! Thanks.

[Richer]

I have no experience using FW clams to clear waterborne algae... but there are other ways of doing it that is a heck of a lot cheaper than what your university is doing right now.

Cheapest way to clear waterborne algae (aka green water) is a complete blackout for 2-3 days. Increase the surface aggitation of the tank, do a water change, cover the tank with heavy blankets or black garbages... anything that will completely block ou the light. After 2-3 days, return everything back to normal, and do another water change. If things stay stable, the GW should not return.

Good luck!

-Rich

[krissyfish20]

The only thing is that these tanks are all situated in greenhouses and it's impossible to make it completely blackout. The tanks are as tall as my shoulders and there are 18 of them in each greenhouse (there are 2 greenhouses). We also would just empty the water and refil it with bow river water (we have a hookup and a hose that feeds us bow river water). For experiment purposes we need to filter this incoming water which isnt usually a problem at all, but because of all the flooding and rain, the water is so full of suspended silt that there is no way we can filter this water at this time. also it would take far to long to wait for all of the silt to settle because we need to get these experiments running because we only have the summer to run them. Under normal heavy rains we are supposed to give the bow 2 weeks to clear to our normal filtering level, not to mention right now its been raining for the whole month of June and now again it's raining. Really our only option (we cant add chemicals either because this is a closed experiment) is to filter the water already in the tanks into a holding tank and then pump the clear water back into the tanks. Plus each tank has to be kept separate (theyre all diff treatments) and water cannot be mixed between any of the tanks.

[christyf5]

Actually there is a way of removing the suspended silt. Put the water in a holding container and then let the silt settle out. Then siphon off the top layer into your tanks.

The problem you guys have is that your populations of critters can't keep up with the algae that is being produced (have you introduced them yet or you just have green water in the tanks?). You could introduce FW clams or mussels, they do a great job but you are also introducing potential contaiminations into your water depending on what you are doing with your critters after they grow (ie. feeding them to larval fish etc).

If you don't have critters in your tanks, depending on how big the tanks are, you can empty them and clean them out, then refill them with unfiltered water and let that sit and then use a siphon hose and gravel vac the bottom.

Just how big are the tanks anyways?

Christy :)

[krissyfish20]

The only problem with the holding tank to settle silt is that we need way too much water for that. We have 26 tanks that are I'm guessing around 1000 litres each. We do have critters in most of them now, and the critters wont be fed to others, but are being sampled and counted every day over the entire summer and used in a thesis about carbon flux and sedimentation rates in lakes. Also phosphorus and nitrogen ratios in dapnia under different conditions and in different nutrient level lakes. We could not possibly do the silt settling thing because we need a huge amount of water and we need it almost immediately or we will not have enough time to get enough data for the experiment.