Greetings All !
Upgrading lighting in a system oftentimes stimulates a bloom of photosynthetic microorganisms. Microorganism populations that were "in balance" with the available energy within the system (light energy + available nutrients within the system's water column & sequestered inside materials within the aquarium) begin to grow exponentially in response to the additional energy provided by the new lights.
Brown populations are oftentimes not actually algae (although sometimes they are), and a purple bloom is almost always representative of cyanobacteria. So the ineffectiveness of an algae remover is not surprising, indeed, it's partial confirmation that there's a strong possibility that what you're looking at isn't an algae. Knowing the general classification of what organisms are blooming is critical to formulating a husbandry response. "General" classification correlations to color are:
Green --> Microalgae
Green --> Macroalgae
Brown --> Brown algae
Brown --> Diatoms
Brown --> Dinoflagellates
Dark Red --> Cyanobacteria
Purple --> Cyanobacteria
It is also perhaps worth noting that microorganism blooms in marine aquaria are rarely a "pure culture", i.e., what appears to be a single type of organism may actually be a diverse community of organisms ... which may require a succession of husbandry responses (as opposed to a single "fix").
If it's a brown algae: In addition to continuing your favorite "algae remover" (personally, I'm not comfortable with adding an algicide to my system although such chemicals can be effective), you can increase the frequency of water changes to knock down the available nutrients in the water column, and you can physically remove the algae as part of the water change process (siphoning).
If it's a diatom: You need to discover the source of the silicon that's driving the diatoms' growth. This may well be your ground water source, so you may need to run it through an RODI unit (as has already been suggested), or you may have to use another water source for mixing your water ... and for topping off evaporation loss.
If it's a dinoflagellate: You'll need to lower the available PO4 (phosphate) that's driving the dinoflagellate bloom. Increasing the frequency of water changes may help with this, but you may also need to incorporate a chemical phosphate binder into your filtration system.
If it's a cyanobacteria: You'll need to lower the available nutrients from the water column (water changes), and you'll need to consider increasing the water flow/turbulence across the surfaces within the tank. Other strategies include carbon dosing (lowering available nutrients by increasing the metabolic acitivity of competing microorganisms) and bacterial inoculation (increasing the biomass of a primary competitor) ... but these last two ought be applied ONLY after you've addressed husbandry and system design issues.
Conceptually ... invasive algae, diatoms, dinoflagellates, and cyanobacteria are ubitquitous ... they're always present within your system, so there's no killing them off (... which is what an algicide is intended to do). Rather than trying to erradicate the microorganisms themselves, what's most useful is focusing on controlling the available nutrients that are driving the blooms. If you can address the excess nutrient issue(s) the blooms will burn themselves out.
JMO ... HTH
