u/Efficient_Smile4360

Hi everyone,
I’m setting up a new tank for my fancy goldfish (oranda and fantail calico) and I could use some advice regarding the filtration system. Here are the specifications:
• Tank Volume: 160 Liters (approx. 42 Gallons).
• Dimensions: 100cm x 40cm x 40cm.
• Current Equipment: I already have a Hang-On-Back (HOB) filter rated at 600 L/h.
I know Goldfish have a heavy bio-load and my current filter is likely insufficient on its own. I'm considering a few options to upgrade the filtration and would love to hear your experiences:

1. Dual HOB Setup: Adding a second Hang-On-Back filter (perhaps another 600-800 L/h unit) to increase turnover and mechanical filtration.
2. HOB + Top Filter: Keeping the current HOB and adding a "Top Filter" (overhead filter). I’ve heard these have great capacity for biological media.
3. Other Suggestions: Should I consider a Canister filter (pricey where i live) instead, or is a combination of the above enough for a Goldfish setup of this size? Or adding sponge filters
   My goal is to ensure crystal clear water and, most importantly, stable parameters (0 Ammonia/Nitrite). What combination would you recommend for this specific tank size and species?
   Thanks in advance for your help!