Yes, true the dirty filter or pantyhose full of established gravel works very well too, but if you gravel clean syphon with a python when you are taking out water there is more than plenty of detritus and bacteria in that water, I have set up many, many new tanks and ponds with that and a sprinkle of gravel. And if you take dirty water from an established pond you will get all that plus the benifitial algae and microinvertebrates, again you can syphon some of the scum of the bottom to get more that enough detritus and benificial bacteria. A must if you want crayfish and mosquito fish, it will also help to handle the poop load of the turtles.
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Jeff Benfer
1.0 pastel Python regius
1.1 mojave Python regius
0.1 normal Python regius
1.3 Terrapene carolina thriunguis
2.3 Terrapene carolina carolina
4.1 Kinosternon baurii
1.1 Malaclemys terrapin terrapin
2.2 double het albino and anerythristicThamnophis sirtalis parietalis
1.0 anerythristic Thamnophis sirtalis parietalis
2.2 Iowa snow Thamnophis radix
0.2 het Christmas albino Thamnophis radix
1.1 double het cherry erythristic, albino Thamnophis sirtalis sirtalis
1.1 melanistic Thamnophis sirtalis sirtalis
1.1 triple heterozygous for amelanistic,carmel, and stripe Pantherophis guttatus
0.1 anerythristic motley Pantherophis guttatus
0.1 Okeetee Pantherophis guttatus