SUN SUN HW-303B-304B CANNISTER + UV LAMP

SUN SUN HW-303B-304B CANNISTER + UV LAMP 

Key Additional Features:

• Self-priming pump — The filter is advertised as having a self-priming mechanism, to reduce the need for manual siphoning. 

• Adjustable spray bar — Allowing better water return distribution / flow control. 

• Media flexibility — The trays allow you to use mechanical, biological, chemical media (e.g. sponges, activated carbon, bio rings) as per your setup. 

• UV on/off / safety switch — In some models the UV lamp is wired so that if the canister is disassembled, the UV cuts out. 

👍 Pros & Advantages

• Good flow & capacity for its price
  The HW‑304B in particular offers a high flow rate (2,000 L/h) which is attractive for larger or heavily stocked tanks.Integrated UV sterilizer
  Having a 9 W UV lamp built in helps in controlling algae, parasites, and bacterial blooms, which can improve water clarity. 

• ** decent head / lift in higher model**
  The HW‑304B’s ~2.5 m lift gives more flexibility where the canister is placed below the aquarium. 

• Multiple media trays
  More trays / stages allow you to optimize mechanical, chemical, and biological filtration separately.

• Self‑priming & adjustable return
  These ease setup and reduce fuss during installation or restart.

👎 Cons, Limitations & Common Problems

From user reports and community feedback:

• Leaks / O‑ring / seal issues
  Some users report leaks or the need to re‑lubricate O‑rings and connectors, especially after opening and cleaning. 

• Lid / clamp stress
  The clamps / buckles that secure the lid can wear or break, especially if you grip them hard to open. Some users say the lid can “stick” strongly due to vacuum / suction. 

• UV plastic degradation / warping
  Prolonged exposure to the UV lamp has been mentioned by users as causing plastic parts (trays) to yellow or warp after extended usage. One user suggests not running UV continuously. 

• Overheating / auto turn off
  Some users claim their HW‑304B would shut off after running a while (possibly thermal protection or fault).

• Air lock / priming issues
  As with many canister filters, air bubbles can block flow until properly bled or primed. Some report weak flow until all air is removed. 

• Noise / vibration
  In some setups, users report noise from water turbulence, suction, or vibration—especially if hoses are not well supported or the impeller is slightly off. 

🔍 Real‑world Feedback & Tips

Here are some community observations + tips:

• “I’ve had the SunSun 304B for about 3 months … I had read that they leak, so I took time to lube the O‑ring … Haven’t had a drop of water lost.”

• “The flow is quite strong … aiming the spraybar helped a ton.” 

   

• “When the spray bar is cheap / clogged, the flow seems weak … cleaning it improved the flow.

• “Lid gets stuck due to suction / vacuum. Disconnect hoses first; O‑ring resistance is expected.”

• “UV warps trays over time; I run UV intermittently, not 24/7.” 

• “The temperature / heat on top becomes warm. UV has been replaced twice in lifetime of filter.”

🧮 Suitability & How It Compares

• The HW‑303B is suitable for medium tanks (below perhaps ~250–300 L in real use) given its 1,400 L/h rating, though actual effective flow will be lower once tubing, media, bends, and lift are considered.

• The HW‑304B offers higher capacity, making it better for larger setups or tanks with heavier bioload.

• The inclusion of UV is a differentiator vs many basic canister filters.

• In comparison to the Dophin filters you asked about earlier (CF12008, CF12308, CF12508), the SunSun units may offer better flow and head in their higher models, but potentially more complexity (UV, more mechanical wear points) and more to maintain.

✅ Summary: Is It a Good Option?

The SunSun HW‑303B / HW‑304B filters with built‑in UV are solid mid‑range canister filters offering good performance and built-in sterilization. If you're comfortable with maintenance (especially ensuring seals are good, managing air, cleaning UV parts) they can be a cost-effective option.