Water Changes In Large Tank?

[andywg]

It doesn't DG, it is the misquoting of scientific papers to try and support a belief.

And to point on water temp, as I have said on other threads, if you have a tap at 6 degrees C (coldest winter mains temp) and a tank at 24, th coldest a 20% water change will fall to is 20.4. That is the furthest it can theoretically fall, in reality it is far less due to filling time and ambient temperature.

I often do 30-40% on my 6x2x2 and it never falls below 20 degrees.

 

[cs091]

I often do 30-40% on my 6x2x2 and it never falls below 20 degrees.

So am I being unduly worried about the temperature dropping? Or would some fish get upset? – And beginners like me should avoid them anyway?

Do you let the cold water in very slowly or let the tap run a little faster?

For instance, how long would it take you to replace 40% of the water in your tank? 150 gallons would make it 60 gallons out of the tap wouldn’t it?

Sorry about so many questions – I didn’t think such a simple question would raise so many interesting replies!

CS - Eager to learn before I get my 1000 gallon tank. (must get bigger house first or give kids away!)

 

[McMurray]

Temprature

Gas supersaturation
Tap water can be supersaturated with dissolved gases (especially nitrogen and carbon dioxide, but sometimes even oxygen), which when exposed to aquatic animals, can cause gas-bubble disease, a condition similar to the bends in divers. Supersaturation is generally problematic only in the winter when the water is especially cold and capable of holding even more gas. This condition is exacerbated when incoming water is pressurized from being pumped. The only treatment for supersaturation is time, which can be lessened with vigorous aeration to drive out the dissolved gasses (a process called off-gassing or degassing) and the application of heat. Aerating water to remove gas might seem counterintuitive, but remember that the water is supersaturated from being under pressure, and aeration at atmospheric pressure will bring the water back to equilibrium with normal air. Heating the water to room temperature will lower its ability to hold dissolved gases. Anyone who has allowed a tankfull of cold tap water to heat-up and observed the formation of tiny air bubbles on the glass is familiar with this process. Similarly, water heated for boiling first relinquishes its dissolved gas as tiny bubbles on the vessel walls before reaching a roiling boil.

 

[andywg]

It takes about 4-5 minutes for all 60 gallons or so to get in (due to the sumps' volumes I am never quite sure how much I change). I have a 12mm hose linked up to the mains and have it on full bore.

McMurray, that is a nice quote from an Amphibian site which points out that colder water has a higher level of dissolved gas. We all know and acceptt this, hence the need for increased gas exchange in hot weather. This does not explain how changing the temp of water and then letting it stabilise (such as heating by kettle and letting it cool) will create gas bubble disease in fish.

Even the link talks about degassing, which is likely to be similar to Chlorine (i.e. coming through a tap and splashing into the water will do the job perfectly) in its ease to get out.

 

[dwarfgourami]

Temprature

Similarly, water heated for boiling first relinquishes its dissolved gas as tiny bubbles on the vessel walls before reaching a roiling boil[/b].

Exactly- the dissolved gas is released. So by the time you have brought it to the boil, poured it into your bucket, mixed it with your cold water, carted it through into your living room and bailed it into your tank, those bubbles will be well and truly gone. They don't hang around you know. Otherwise, boiled water would be bubbly, like Coke. When did you last have a fizzy cup of tea?

 

[andywg]

Aaah, double post (silly router!)

 

[Tolak]

Andy; I'm wondering where you are getting this info about not needing to dechlor water. I buy Prime in bulk, have chlorine & chloramine in the water. I've done 50% wc's without dechloring, I waited a few hours before adding dechlorinator, then added the proper amount. No ill effects were noted, I just got tired of watching the tank with one eye, the tv with the other.

As far as water changes go I have 450 gallons between 16 tanks ATM. I have several 5/8" I.D. siphon hoses with pvc on the end to siphon the bottom of bare tanks. These go int a 35 gallon Rubbermaid can with a 1400gph pump that drains through a hose across the basement to the sump pump. A second hose is used for filling, I can drain & fill tanks at the same time. I do mix hot & cold at the tap, but I am doing 50% to 80% water changes, on tanks that are around 80-85F. 50F tap water would do a number on the fish. Declor is added on the fly as they fill, either before, during, or after, depending on what else I am doing at the time. Multi-tasking with several tanks keeps my mind sharp, and reflexes quick.

 

[andywg]

The best info I have on non-dechlor is from another forum where a member has measuered their tap water (4-5ppm chlorine) then his tanks after a 50% water change (0.25 ppm chlorine) and again 5 mins later (0ppm chlorine).

Another did the same, though they have chloramine and noted the same sorts of results. It is actually believed that the ammonia in the chloramine may actually FEED the bacteria in the filter rahter than kill them. Once the bacteria utilise the ammonia, the chlorine is gassed off quickly as above.

However, it was noticed that more immature tanks (less than 6 months old) could take up to an hour to clear the chlorine/chloramine, more established ones needed far less (5-10 at most).

We all know that chlorine gasses off very quickly, and if chloramine can actually be used by the bacteria (something which has been noted by human waste processors) then de-chlor could go the way of aquarium salt.

I would love to see some actual scientific research in it, but there is not one scientific test on the effects of chloramine on the types of bacteria (Nitrosomonas spp or Nitrobacters spp, depending on which source you read) found in a filter.