Water Quality
by Dr. Adrian Lawler
Extracted from the staff Operational Handbook which Dr. Lawler wrote as Aquarium
Supervisor for the J.L. Scott Education Center and Aquarium, of Biloxi, MS
Aquarticles
A volume of water (tank, pond, etc.) must have proper conditions to support life in a
healthy state and a minimum of things (or toxins) detrimental to aquatic life. Poor water
quality for one species may be all right for another species; there may also be a wide
range of tolerance of a species to water quality parameters.
Oxygen - For most species it is best to have five ppm oxygen or
greater in the water. Our air is supplied by blower, changed once per week. Blowers are
kept running in power outages by our generator. Air to various tanks can be adjusted by
valves. Air to tanks is constant and sufficient, so oxygen readings are not necessary.
Temperature - Water temperature in our tanks is ambient and slower
changing than the air temperature around aquarium, and is usually in the range of 72-76F.
Water temperature is not controlled in any tank at present, but higher temperatures than
ambient are obtained by having lids on tanks with lights above.
Salinity - We have two main mixing tanks, one for fresh water and one
for salt water of about 21-25 ppt. When lower or higher salinities are wanted, add
filtered fresh water or more sea salt. Add no more than five per cent city fresh water as
make-up water to top off tanks low due to evaporation; if more than five per cent of tank
volume is needed, use filtered fresh water. We try to keep salinities on the low side to
save money on sea salt. Salinity readings are taken with a refractometer.
pH - Rapid changes in pH are avoided by not doing major water changes;
pH tolerance will vary per species. The range of pH for freshwater fish is about 6-9; for
salt water fish the range is about 7.5 - 8.5. Tanks with logs will need more frequent
water changes and charcoal filtration to minimize pH drops and brownish coloration of
water. Saltwater tanks will need periodical addition or replacement of crushed coral for
buffering. Litmus paper or a pH pen are used to measure pH.
Trace Elements - Replenished by water changes, trace element blocks
(P-5), or addition of elements needed (KI for iodine removal by growing animals).
Chlorine - Removed by charcoal filter on top of mix tanks, or various
commercial products.
Ammonia - Removed from city water by use of zeolites prior to addition
of sea salt.
- Ammonia can build up for various reasons in display tanks (see section on water
changes). Readings of tanks are done periodically using Kordon test kits; kits are not
very accurate and presently read about twice the actual reading. Corrective measures
(water changes; AmQuel + re-seeding) should be initiated at readings higher than 0.3 ppm
(= actual of about 0.1 ppm).
Nitrite - Allow no more than 0.1 ppm nitrite in tank water. Test with
Kordon test kit. Water changes and re-seeding should be done.
Nitrate - Although some fish can tolerate nitrate of 1000 ppm or
higher, Spotte (1979) recommended nitrate concentrations of no higher than 20 ppm for
aquariums. Reduce levels of nitrate by water changes and incorporation into living plants
(let algae grow in tank except for viewing window).
Dissolved Organics - Yellowed water containing dissolved organics can
be cleared up by water changes, use of charcoal, or foam fractionation (=protein skimmer;
will not work well in freshwater).
Organic Debris - see section on python/siphon. Organic debris must be
periodically removed by sand, DE or other type filter, by python or siphon, or by opening
bottom tank drain.
Toxins - Remove using charcoal (then discard) or by water changes.
Reference: Spotte, Stephen. 1979. Seawater Aquariums, the
Captive Environment. John Wiley & Sons, New York. 413 p.
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