Under gravel filters

[HermesGSP]

Would an under gravel filter with two power heads be recommended with 2 gps's in a 55 gallon long? Thanks.

[G S P Freak]

Under gravel filters are immense detritus traps that are extremely hard to clean. I'd avoid them at all costs, but that's my opinion.

[RTR]

IMHO, a 55 is only a temporary home for two GSPs, I would suggest a 75 minimum. Whether or not UG is a detritus traps does depend on how they are used and maintained. That is true for any filter format. I would guess that the large majority of the folks using UG have no clue as to how to maintain them. Personally I like UG (usually in the form of OE-RFUG) and have some which have been in constant use in the same set-up over 20 years. Those tanks have superb water conditions and are quite easy to maintain.

However, I would not recommend even OERFUG for GSPs, as they really should be in SW as FOWLR + skimmer + lighted macroalgae refugium. The up-front investment is more, but the next 10-15+ years upkeep is far cheaper and easier. Conventional bacterial biofiltration is out of date for SW. Its operating cost is too high for what it does.

HTH

[HermesGSP]

Ok thanks. Rtr, I read your article on UG right after posting this. Very informative. Just to be clear, why do you not like UG for full marine tanks? Is filters, skimmers and live rock enough?

[bertie 83]

Live rock, skimmer and 24/7 lighted refugium tends to be the best way for marine. Canisters and such tend to be nitrate factories.

[RTR]

+1 to Pufferpunk"s comment above. She got it in one shot.

Nitrification is good in FW and low BW, as nitrate is less toxic than ammonia and nitrite, and FW and low BW are inexpensive, so we do large-scale water changes to get rid of nitrate. SW is expensive. FOWLR (which does both aerobic and anaerobic nitrification and denitrification) + skimmer + 24/7 lighted macroalgae refugium are long-term investments which are cheaper than large weekly SW partials.

HTH

[Pufferpunk]

LOL, I don't see a comment from me.

[Biff Malawi]

Yup I went back twice thought I was crazy, then I thought you removed it PP and was wondering what you posted. LOL

[bertie 83]

I had to look back too, he had not long commented after another of pps posts I believe.

[RTR]

OK, I substituted PP for bertie - mea culpa! mea culpa! Apologies to both PP & bertie.

I scrambled the names, but the info still holds.

There are uninformed hobbyists who consider UG to require little or or no upkeep. Thst is a huge mistake. Conventional UG requires very high upkeep. Any untended (filter medium not regularly rinsed) is a detritus reservoir. That is true whether the filter is HOB, canister, UG, RFUG, air-driven sponge, whatever filter type excepting fluidized beds if they are properly designed. And fluidized beds are biofilters only, they have no debris holding function. Particulate capture and removal and biofiltration are equally important functions, but they are not synonimous functions. Any untended mechacanical or biological filter can become a pollution generator.

Mechanical/particulate filters trap organic particles and debris so that they can be removed from the tank by rinsing) before they are digested by bacteria and infusoria.

Biofilters render hazardous dissolved materials safer by bacteria changing them to less toxic forms (primarily nitrification).

Skimmers segregate dissolved proteins and some fats/oils (both labeled dissolved organic compounds, DOCs) from the tank water.

Lighted refugia remove nutrients from the water column as algal mass (periodically harvested) and serve as refugia for 'pod generation.

Live rock performs both anaerobic and aerobic nitrification. The former removes nitrogen from the system as N2 gas. The latter changes highly toxic ammonia to much less toxic nitrate.

HTH

Deep sand beds (DSB) do nitrification at shallow depths, gaseous denitrification at greater depths.

Plenums are shallower than DSB, but do gaseous denitrification. Their safety margins are better than DSB, which can be toxic if disturbed. They also require much less tank space. Both DSB and plenums are relatively slow to eatablish.

[sgtmyers88]

LMAO at the mix up. That made my day. I was looking for PP's comment to see if it got accidentally deleted or something. It's okay RTR, it will probably happen to all of us at some point.

[Pufferpunk]

Long ago, when I ran UGFs, I used to take a long hose & siphon out the debris under it.

[RTR]

I don't see the same text you do. I an visually handicapped and need to use special programs for low-vision folks to see the web, and CCTVs for books, and handheld CCTV if I want to see prices or labels in stores. It is a PITA, but 'way ahead of not being able to read at all. The upside is that I don't have to pay bills myself, or do the taxes. I admit that most fiction books are audio books from the LOC, NLS. I still do some gardening and all the tank care, but the big chores are farmed out.