In my last post, I wrote about the tragedies that can result when you fail to put netting over the filter intake soon enough. Unfortunately, that's not the only problem you can encounter with netting.
On Monday, Emily Burlett, at Rutland Intermediate School, submitted this report:
I'm having some difficulty with my fish getting stuck in the filter. At the beginning of last week I found almost 25 in the bottom of the filter (alive & dead). Since then I have been losing them quickly ( I'm thinking getting stuck in the filter may have stressed them out). I changed the screen on the filter intake but still have several getting stuck to it.
Later in the day, Emily responded to one of my questions with this:
I used the mesh that you gave out at the training to cover the intake but they got through it. I have attached a picture of the filter intake with a piece of screen I used for modifying the breeder baskets( I changed from the mesh to the screen after I had to fish all the fish out of the filter).
Oh, no! It was my fault! Emily was using the netting I passed out at the TIC workshop!
Then yesterday I got this e-mail from Colby Hescock at Rutland Town School:
Everything has been running smoothly here at RTS! Unfortunately we discovered that we lost 6 fish because they got sucked up against the filter. We have netting around it to prevent them from being sucked into the filter, but they still manage to get stuck to the outside and aren’t strong enough to swim away. Here’s a picture of our current set up, I was wondering if you had any suggestions? Let me know, thanks!
Here's what Colby's filter intake looks like.
Later in the day, Colby added this:
The trout are getting sucked against [my emphasis] the netting not all the way into the filter, I think our netting is working fine to keep them out. The problem is the sucking power of the filter is too strong when they get in close enough.
These problems are due to one or both of these two possibilities:
When I shared this problem with Maryland TIC coordinator Chuck Dinkel, he mentioned that most filters in use have a flow adjustment setting that would allow a teacher to reduce the flow, thereby making it less likely that a weak swimmer would get sucked up against the netting. You have to be somewhat careful in reducing filter flow because it could compound any water chemistry problems you might be having; but if your water chemistry is okay and your fish are losing the battle with the filter suction, try reducing the flow for a while.
If you don't know how to change the flow setting, check your filter manual. If you no longer have a manual, you can probably find one on the Internet. If you use either the AquaClear 110 or the Fluval 406 filters, I have put copies of those manuals into this folder on the VTTIC Google Docs site.
So what's the take-away?
Because netting should be neither too coarse nor too fine, it's been hard to describe the netting you should install over the filter intake, so I've worked on that. This afternoon I measured and photographed netting that I think should work just fine. What you'll see below is nylon screening (made for screen windows and door) that has 18 squares per inch. I think that should work very well. I bought this at my local hardware store.
Great video from MMS
Meaghan Beley-Finnemore, of Milton Middle School, sent me this nice video. Her fish look great! Healthy, active, and fat. I also like the artistic tank background. Is that a baby otter I see there?
Meaghan also had a concern about cloudy water. I responded to Meaghan with the following:
Here’s what the national TIC site says about cloudy water:
“The water in my tank is cloudy. What should I do?
Cloudy water probably indicates an excess in decaying matter. This may be from dead fish, leftover food, or a problem with the filtration. Carefully conducting regular water changes, as well as cleaning the tank of all solid material, is the best way to fight this. Make sure the filter is functioning properly, and that water is flowing out of it. Clean filter components if needed, but do not use soap or any chemical cleaners. Carbon filter packs should be replaced every year. If fish are not eating all provided food, you may reduce the amount given until they are able to eat it all. Excess food after 10 minutes should be removed and discarded.”
This is a good opportunity to remind or tell you about the Troubleshooting folder on the national TIC Web site. You can often find answers to your technical concerns there. Below is a screenshot of the Troubleshooting page. The image is also a link to the folder. (While you're at the national TIC site, check out the other great resources there, including curriculum ideas.)
Water chemistry worries
Several teachers wrote with concerns about elevated ammonia, nitrite, and/or nitrate levels. I'll try to provide an overview of what to accept.
Overview. It's normal to see all these three chemicals increase as part of the "nitrogen cycle." The first two are the most potentially toxic for brook trout. Nitrate, even at fairly high levels, causes little harm. Fry urine and decomposing feces and excess food contribute to ammonia levels rising. Nitrifying bacteria in your filter and elsewhere convert ammonia to nitrite. Denitrifying bacteria, also in your filter, convert nitrite to nitrate. Nitrate levels are managed by water changes.
When the nitrogen cycle proceeds "according to plan," this is what you can expect:
Unfortunately, many schools experience deviations from this classic sequence of processes; and, thanks to Robb Cramer, one of our eastern schools engaged in a "pre-cycling" process so presumably saw had all of this happen before their eggs arrived.
So how do you manage water chemistry?
Finally, it's also important to observe your fish closely. Are they active and feeding enthusiastically, or are they listless and languishing on the bottom? Do they look "normal," or have you observed a change in their appearance (a change in coloration or perhaps reddened gills)? Sometimes water chemistry reading seem to be a concern yet your fish look great. In general, if your fish look great, you don't need to panic.
Thanks to Amy Wright (Fair Haven Grade School) and Meg Ritter (Crossett Brook Middle School) for sending pictures in the last few days.
Joe Mark is Lead Facilitator of Vermont's Trout in the Classroom program.
In June 2012, I retired after 40 years in higher education, having spent the last 32 years of my career as dean at Castleton. One of the first things I volunteered to do in retirement was to work with a parent-friend to help the Dorset School, where his kids and my Vermont grandkids attend, start a TIC program. Gradually that commitment grew into my current role, which is both demanding and highly rewarding.