Jeffww, that is a very good topic.
A systemic treatment of chemicals could easily eliminate the algae problems and as long as no other filamentous algae are introduced to the tank via fish or plants (easily preventable) then the problem is done. And it's done for good.
Unfortunately that approach doesn't apply to all algae. Let me provide two constrasting examples:
(which technically isn't an algae at all, but a photosynthetic bacterium) can be easily and completely eradicated from an aquarium using erythromycin. If eradicated, it will never return - even if conditions are perfect - unless reintroduced.
Back when I joined this forum seven years ago, it was seriously frowned on to use erythromycin. Use the natural approach instead. Eliminate dead spots with low oxygenation by improving flow, increase nitrates, and use a three day blackout.
The problem is it often didn't work. Some people kept doing blackouts over and over, and the BGA wouldn't be killed or would rapidly reappear; while the plants suffered progressively more with each blackout, leading to other problems. It was a sad situation really, and I sympathized with the frustration of everyone who went through this.
The natural approach just isn't very practical. There is nothing magic about three days of darkness that guarantees 100% BGA kill. Furthermore, there is no such thing as an aquarium without dead spots; show me one, and I'll show you an empty tank! Yet people defended this approach to the end.
Fortunately, erythromycin is more acceptable today. But look how long it took to gain the current level of acceptance.
is different. It cannot be totally eradicated from an aquarium by any means that will leave anything else left alive. If the aquarium becomes "unbalanced", it will always rapidly return without reintroduction. Or perhaps it's so pervasive in the environment surrounding the aquarium, that it is constantly reintroduced; same end effect.
Assuming there is some chemical that will successfully control GSA in an aquarium, it would have to be used constantly. That is obviously undesirable, because all algeacides are toxins by nature. It's just that they're slightly more toxic to undesirable life, so by using them at the correct dosage, we can kill selectively. But increase the dosage, and everything dies; or use them for too long, and there are likely cumulative health issues for your livestock.
What about the other algae?
Let's assume most can be truly eradicated. They will not come back unless reintroduced. To avoid reintroduction, you must never import any new plants to the tank.
I operated in a vacuum like this for years, and found that I had actually seemed to eradicate several algae types I previously had through natural means alone (good balance). Of course, sometimes I'd mess up. But no matter how far I let the balance slip, the only thing that appeared was GSA and GDA; and a bit of BBA on hardscape, but never on plants.
Of course, eventually I wanted some new plants. And they contained several new types of algae. Some of them appear to have been truly eradicated. But to this day, whenever I slip badly, Staghorn also pays a visit.
But aside from that I also believe it's because of the whole mentality of "this is slice of nature. It is a nature aquarium."
"Natural" is a banner that people wave, without truly understanding. Yes, the plants and animals in our tanks are from nature. And yes, they have natural needs, which we fulfill. Furthermore, by taking advantage of certain natural interactions, we can have more stable, maintenance-free, enjoyable tanks.
However, how often do you hear:
"We should emulate nature as closely as possible!"
"We should do this or that because that's how it works in nature, so it should work in our tanks!"
I tell them go ahead. Let your tank freeze over in the winter. Randomize the lighting schedule to account for overcast conditions. Change water at random to account for rain. Let fish breed to overpopulation. Let disease run its course without medication. Make sure every flora/fauna combination in your tank is one found in a natural ecosystem, rather than cherry-picked from various habitats from around the world. Try to set up a self-sustaining ecosystem in a tiny glass box so you don't have to add any food. Don't ever trim the plants. And let algae grow at will.
The truth is, every one of us bends nature to our will in our tanks to achieve a desired effect, far more than we care to admit.
They have no answer for that other than ignoring it and continuing to cry "Natural is good! Natural is beautiful! Natural is best!" And dealing with that kind of pervasive ignorance and dogma is quite irritating.
Especially when it blocks progress and enjoyment of the hobby.
As an example, take Algaefix. I admit it's a pretty nasty algaecide. It kills algae. It kills shrimp. It sometimes even kills fish. But the bias and outrage against its use is so great that people won't even consider alternate uses.
I was faced with the task of saving a mass of java moss infested with invasive cladophora. That algae is tough. It isn't killed by any dose of H2O2 or Excel that won't also kill the moss. It also thrives in the same conditions as plants, so it can't be cured by balance.
Faced with the prospect of throwing all my moss out, I hit on a new idea of using Algaefix outside the tank, as a dip. The result was dead clado, java moss in perfect health. And no risk to my fish, since it was never used in the tank. Since then, I've found the same method works equally well on some other algae as well.
So I've discovered a very useful dip, which is spectacularly effective against many algae. It doesn't damage plants like other dips frequently do. It can be used to salvage plants that are normally unsalvageable, or to remove algae from new plants before they are introduced to your tank. You'd think people would be all over that, like my idea to use Excel as a spot treatment (yep, I introduced that). Right?
Wrong. I drop the suggestion every few months. It's not catching on. Algaefix=bad!
Oh well. Maybe in another seven years?