Hello, Im having a few problems with my tank. First and most importantly im having a serious PH problem. I do a 30% water change every week and the PH drops from around 6.8 after the water is added to 5.5 in a day or two. I have a 90 gallon aquarium with flourite susbstrate, some drift wood, two big sword plants and some vals and other small plants. I have a new fluval 405 canister filter but it has the old biomedia in it from the old fluval canister filter i had. I have a CO2 system but it is not and has not been on yet because of the PH problem. I recently got it but the tank itself has been set up for a long time. I looked around and i found a forum that said it could be a KH problem. I dont use chemicals in my tank and i dont think its been getting fertilizer recently but i lost all 3 of my wild discus and 2 tank bread ones as well as the female angelfish out of my breeding pair. If anyone knows a good way to fix this any information can help. I also have a problem with the brown growning on my plants and killing them. Ive been super busy with college so my dads been taking care of it but im on break now so I want to fix it before i lose anymore fish. I was told the co2 system would help with the algea but i cant turn it on until PH is stable. I live in the suburbs of CT if that helps i think the PH of my water is actually a little high right now with the house filter system we have on it. If any more information is needed i can get it when i get back from work. Thank You for any help you can give.

It could be the natural ph of your water. Try taking a sample of your tap and setting aside. Test it when you first set it there and test again 24hrs later. Ph usually rises when you do this, but when I make RO water, that water drops another .3-.4 in about 12hrs time. This is just to rule out the possibility.

Water with a low KH (3 degrees or less) is subject to PH swings as you have described. KH is an acid neutralizer and it buffers the PH from dropping rapidly. Seachem and API both make buffering agents using natural ingredients. Their is also a home made receipe using sea salt, epsom salt and baking soda but I'm not sure of the ratios involved.

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Do fish get thirsty?
How to fishless cycle your aquarium http://www.aquariumforum.com/f66/fis...cle-15036.html

Information on API FW test kit http://www.aquariumforum.com/f2/api-...ion-15347.html

Have you tested your kh? I would do that before you add anything to alter your ph.

jrman is quite right.. do a kh test of both your tap water and the aqarium water. do a ph test on both also after the tap water has sat around overnight. If you find you need to use it, get the seachem products. They have a fair amount of helpful minerals in them as well as being able to buffer for a longer period of time than you'd get with just baking soda. If you do use any products for this purpose, use them very slowly so you dont kill whatever fish you have left in your tank. since you said you had discus fish, you may try the "Discus Buffer" as well as "Discus Trace" to properly balance your water for those fish. here's the info on the products Seachem Freshwater.
If you decide to use other products, follow the procedures very closely (if you use something like an acid regulator with a neutral regulator) and do you math precisely while testing after each increment.

pH and KH are related with carbon dioxide. Higher carbon dioxide lower pH.

One thing to consider is balancing out the tank with thriving plants to suck the carbon dioxide from the tank.


my .02

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

Ok the pet store didnt have anything to test it O.o. So it should be in today and ill get it to test the tank water as well as the tap water. I dont add anything like start right or a chlorine remover just as a side note. Id rather not use a chem that i have to keep adding or keep an eye on. I heard that crushed shells might work? would crushed shells or coral in my filter be a good fix? Just as a summary I have low PH without using my CO2 system, tank is planted, and PH changes r drastic, PH from tap is a little high i believe. Ill be able to test everything tonight though.

Also if this problem was solved on another post please post the link here. Im new to this website and im still trying to figure everything out.