"But Jeffrey, I still have some GSA/BDA/diatoms on my rocks/wood/glass/plants and I can't use Glut to get to it and I consider it the most unsightly thing"
Never fear my good friends, there is yet one LAST resort.
Animals!
First and foremost, you should really try every other method first. Animals cannot control an unbalanced tank...they simply can't eat that much. On top of that, there's a limited number of fish you can put in any one tank, so you should think long and hard about if a particular fish is worth the space/water chemistry simply to eat algae IF there are other things you can do instead.
However, once you've thought about the ramifications of adding another animal to your tank, there are several options and they all have their ups, and many of them have some BIG downs.
Otos: These are your go-to. Otos primarily eat GSA, GDA, and diatoms, but I've even seen them munch on wee bits of BBA and string algae. They are small and don't contribute significantly to your bioload. Generally, they are fairly cheap. The downside is that they tend to be sensitive fish. Large pH/TDS swings will wipe them out so you need to acclimate carefully. Also, if you accidentally adjust your co2 too high, these will be the first to go. The other downside is that, if you have a considerable amount of GSA/GDA/diatoms you'll need a lot of otos to handle. Otos are nice at controlling that last 2% of algae that your co2 and glut just can't wipe out. Otos need supplemental food as well. Algae wafers, veggies, and spirulina flake are good treats every few days. Otos rarely successfully breed in a community tank, so therefore you'll need to repurchase them every few years.
Amano shrimp: Amano shrimp are algae destroyers. They eat everything: String Algae, Clado,BBA,GSA,GDA....the list goes on and on. On top of that, they munch on detritus as well. Amanos are some of the largest FW shrimp. No matter how many Amanos you have, their contribution to your bioload is insignificant. Generally, for algae control (if there is nothing else in your tank working on the algae) you'll need 1 per gallon. The downside of Amano shrimp is that they are fairly pricey, especially considering the whole 1 per gallon thing for total algae control. The other big downside is that they don't breed in FW, and even in a brackish environment, captive successful breeding is incredibly rare. You'll have to replace these guys fairly regularly. They don't really require supplemental feeding as long as some of your food from regular feeding makes it down to the substrate for them to clean up later. If you want to give them a treat, foods like those for Otos are nice.
Red Cherry Shrimp(or any shrimp easily bred in captivity): RCS/Tigers/Snowballs/etc are a great form of algae control. Most people don't think of them this way, but let me explain. When it comes to algae eating shrimp, you really can't beat the Amano shrimp....but dang if they aren't expensive to keep a population. Well, individually, these other shrimp don't put near the hurt on algae as Amanos do, but they are DIRT CHEAP and breed like rabbits. These shrimp primarily munch on detritus, diatoms, and left over food, but once a healthy population gets going, they'll eat string, clado, bba...pretty much anything. It's hard to list a downside to these guys. I suppose the major downside is that they aren't a cure-all for algae and that keeping them can limit what fish you have, because if a shrimp can fit in their mouth, they'll eat it. However, in a heavily planted tank, if you introduce breeding shrimp BEFORE you introduce fish and get a population going, you'll have no problem keeping them. The other benefit of breeding shrimp is that they can be a healthy snack for fish. I suppose I'm a little too over eager about them, but they are just great additions to the planed tank.
Nerite Snails: Of all the algae eaters on this list, Nerites almost take the cake. They are real work horses. Anybody that thinks snails move slowly has never watched a Nerite....ok, that's a bit of an exaggeration, but these guys chug along compared to other snails. They eat EVERYTHING and I mean EVERYTHING. Diatoms, detritus, BBA, GDA,GSA, Clado, String...I mean EVERYTHING. They'll work on the easier to get stuff first, but once that's gone, they'll start in on the BBA, clado, string and have that gone before you know it. These things love to eat. However, there are downsides. For starters, Nerites typically start at $1.50 each for Olive Nerites and work their way up for larger/more decorative species. Like Amanos, for complete algae control, 1 per gallon is a good number. Also like Amanos, they can't successfully breed in FW and, while I've seen efforts, I've never read about any successful captive breeding even in brackish environments. Another thing, and this is the real kicker: They don't live long in soft acidic environments. For most of us living in Atlanta and for anybody that injects CO2...this means your tank. Their shells slowly get eaten away by acidic water. You can help them out by giving them food intended for snails/inverts with calcium, and you can make sure you're water doesn't get too soft...but their's no stopping fate.
These are your miracle workers. You can go with any of these, but I personally "use" and recommend a good mix. A good mix of the above will control that last bit of algae down to the point that you don't even notice it. For example, in my 120g, I've got 35 olive nerites, 30 otos, and 60+ RCS. I had a 45g tank with 8 Otos, 12 nerites, and 20 Amanos. A 75g with 30 Amanos, 50+ RCS, 15 otos....you get the idea.
Honorable Mentions: Believe it or not,
Mollies and
Platies are pretty good algae eaters. They munch on GSA, GDA, String, BBA, and Clado. The upside is that they are dirt cheap. The down side is that they breed a lot (so that they are dirt cheap). They'll eat algae, but they'll also take over your tank if you'll let them. If you decide to go this route, just find someone in your local club with a wolf fish and send the fry over their way
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