Filtration

Internal Filter

Internal Filter buyer guide. Submersible all-in-one filter for tanks where back-clearance is limited.

Internal Filter TL;DR

Price range: $15-$60.

Submersible all-in-one filter for tanks where back-clearance is limited.

How internal filters work

Submersible all-in-one filter for tanks where back-clearance is limited. Mechanical filtration captures particulates, biological filtration hosts nitrifying bacteria, and chemical filtration uses media (carbon, GFO, resins) to remove dissolved compounds.

Sizing for your tank

Rule of thumb: pick a filter rated for 4-6x your tank volume in gallons-per-hour turnover. Oversizing is safer than undersizing - cleaner water, more nitrifying surface area, more headroom for stocking growth.

Setup and maintenance

Rinse mechanical media in old tank water (NEVER tap water - chlorine kills bio-bacteria) every 2-4 weeks. Replace chemical media (carbon) monthly. Bio-media is permanent - never replace unless physically degraded.

Common internal filter mistakes

Replacing all media at once - destroys the bio-filter. Rinsing in tap water - same result. Skipping pre-filter sponges - shortens main media life. Buying undersized for the tank - leads to ammonia spikes.

Cost expectations

Internal Filter runs $15-$60 new. Used units in working condition: 40-60% off. Replacement media adds $30-$150 per year.

Internal Filter FAQ

Is a internal filter good for a beginner?

Yes - sized appropriately, all major filter types work for beginners.

How long does a internal filter last?

5-15 years with normal use; impellers and seals are wear items.