Cultivation of the red macroalga Asparagopsis is gaining momentum as a source of methane reducing feed additives and for nutrient bioremediation, with current farming focused on the tetrasporophyte stage. Advancing Asparagopsis cultivation offers significant environmental and economic benefits. Tetrasporophytes are vulnerable to epiphytic contamination by filamentous algae, adversely impacting both productivity and product quality. This study employed morphological and molecular analyses to identify an unknown red macroalga, growing epiphytically on Asparagopsis taxiformis tetrasporophytes, as Colaconema cf. infestans. Colaconema cf. infestans infestation has the potential to disrupt Asparagopsis farming and impose significant operational and economic costs. We employed a systematic approach to evaluate 57 treatments derived from nine chemicals for eradicating C. cf. infestans from A. taxiformis tetrasporophyte cultures isolated from Queensland, Australia. Initial screening with pulse-amplitude modulation (PAM) chlorophyll a fluorescence revealed a differential tolerance to chemical treatments between the two algal species, at both one day and one week post-treatment. A subsequent four-week co-culture experiment assessed the efficacy of 13 chemical treatments. Only four treatments (ethanol: 50% for 10 seconds, applied twice per week, and sodium hypochlorite: 2% for 5 minutes, applied at any frequency) resulted in an absence of visible C. cf. infestans contamination across all replicates. However, these treatments also caused significant Asparagopsis bleaching (98.8–100.0%) and thus do not represent a viable solution for contamination management. In the absence of an effective solution, this study emphasizes the importance of regular monitoring to allow early detection and explores potential future strategies for contamination management.