I had my L2 set up on my 90 gallon reef tank for over a year with a nice algae mat until 3 weeks ago. I have my unit on a secondary loop in my sump with a separate pump. I turned off the pump to do my weekly cleaning, got interrupted and you guessed it--I forgot to turn the pump back on. Didn't notice it until the following week, by which time the algae was a dead moldy mass. I used the scraper to remove the dead stuff off the surface of the screen and put it back in, hoping I would get some grow-back, but no dice. After two more weeks I have a few dime-sized patches of green. I'm wondering if I should use a brush to clean out the holes in the screen, which are currently clogged with dead stuff, to give the new algae a better foothold on the screen. Any thoughts?
I had that happen twice on a tan running an L4, the first was when someone shut off a power strip for some reason, then just a couple months later the pump stopped working. Both times the screen got cooked. The result was a kind of baked-on white crust on the screen that I thought would make a great substrate for re-starting, but it's not that good actually. The first re-start took forever to get growing again, the second time it was actually a bit faster and I got a nice big harvest, but almost all of it came off during cleaning and it is like starting over again. I would scrub the dead stuff out for sure. I'm considering that once a screen gets cooked bad enough, it's toast. The best way to re-start a screen in my opinion is to just soak it in vinegar, maybe make a quick pass with a saw blade to rough it just a bit (not so much that it tears...you have to be careful about that when re-roughing!) and then do a mortar coating (and cure & soak). The mortar screen starts up very fast, so the time it takes to cure and soak is more than offset by how quickly it initiates growth.
Thanks for the quick reply. A few questions: 1. How long do I soak the screen in vinegar? 2. What kind of saw blade--will a hacksaw blade work? 3. I looked up mortar coating in the Knowledge Base section of the site (never heard of this before)--after I coat, cure, and soak the screen as directed, I can actually put it back in the scrubber and run it without harming my fish or corals? Or do I have to run it outside my system to build up an algae coating first?
1) soak for maybe and hour, then scrub with a stiff brush, repeat as needed 2) I use a sharp toothed saw blade Don't press to hard, it's already done once you just want to get it a bit prickly again. I usually rough these up enough that you may not need to re-rough, so you may not need to do this, but it depends on how vigorously you scraped the screen when cleaning. 3) yes. People use mortar all the time for DIY rock, the primary thing is you need to soak it well so that you leech out any bad stuff. When doing DIY rock, that means 6 weeks, but that's because you are working with thick material. This is only a very thin mortar coating, so if you put it in a bucket (for an L2 screen, and 1g bucket will work) and then change the water daily for a week, you're good. I hang mine with zip ties from a pipe over a utility sink and run a very small pump pointed towards the top of the water to agitate, and let that go for 2-3 days & change the water once and that's all you need. You do not need to grow algae on it prior to using it in your system after soaking. I started using this technique earlier this year and have had zero issues reported (and I've been using it on my tank also). The mortar just creates a very microscopically rough surface that algae grow on quickly, then it slowly breaks away during harvesting and allows the plastic canvas to be exposed and cure like before (without the mortar). The canvas is very slow to mature, the mortar is fast but sacrificial. FYI I got the idea from Paul Baldassano (the guy with the 40+ year old reef tank, RC and R2R, inventor of the Majano Wand, writes books and articles about reefkeeping, prefers supermodels, etc)
I have new number 7 canvas material on hand, would it be better if I cut a new screen and mortar coated that one to make sure its clean, or is the age of the old screen a positive factor (its been in use for 15 months now).
I'm not sure if it really makes much of a difference. I think you could just add a mortar coat to the old screen after soaking in vinegar and scrubbing it with a brush. No need to re-rough, that's actually likely to just result in tearing. The mortar gives it the rough surface to initially bond to, the "prickliness" of the screen is just a surface area thing, microscopically it isn't really that rough at all - which is why it takes 4-6 weeks for algae to attach, no matter how well you rough it up.
Finally got a small bag of mortar mix in the mail (you'd be surprised how hard it is to acquire mortar in Manhattan). I am going to soak the screen in vinegar tomorrow for 3 hours and then brush it and coat it with mortar. I read the update in the Screen and Fasteners section of the site, so I am going to follow that curing method and sandwich it between two pieces of wax paper covered with a wet towel, spraying it with water a couple of times a day for 3 days (BTW, do you spray both sides?). Then I will soak it in distilled water for a week, changing daily. Did I miss anything? Is this overkill? I have a small 40GPH pump, so I could hang the screen in the bucket and agitate for 3 days as you suggested to shorten the soaking period....
go to stage 3 here for the mortar application You don't really "brush" it on, you want to rub it in. I've found that just a day or so is good enough for the curing time (about 24-36 hours) and then you can go straight to soaking it. Tap water is fine for soaking, place it in a 1g or 5g bucket, change the water daily, swish it gently a few times a day, do that for 4-5 days. I hang mine in a utility sink and use a small pump (eheim compact 1000) dialed back to about 1/4 flow and pointed straight up at the surface (so the pump isn't jetting right on the screen) and that does the trick in about 2 days (lots of water volume helps) but in a bucket is just fine.
